def arch_recursion_python(parameters, resids, sigma2, p, nobs, backcast,
var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters
resids : ndarray
Residuals to use in the recursion
sigma2 : ndarray
Conditional variances with same shape as resids
p : int
Number of lags in ARCH model
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : 2-d array
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
"""
for t in range(nobs):
sigma2[t] = parameters[0]
for i in range(p):
if (t - i - 1) < 0:
sigma2[t] += parameters[i + 1] * backcast
else:
sigma2[t] += parameters[i + 1] * resids[t - i - 1] ** 2
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def _ar_forecast(y, horizon, start_index, constant, arp):
"""
Parameters
----------
y : array
horizon : int
start_index : int
constant : float
arp : array
Returns
-------
forecasts : array
"""
t = y.shape[0]
p = arp.shape[0]
fcasts = np.empty((t, p + horizon))
for i in range(p):
fcasts[p - 1:, i] = y[i:(-p + i + 1)] if i < p - 1 else y[i:]
for i in range(p, horizon + p):
fcasts[:, i] = constant + fcasts[:, i-p:i].dot(arp[::-1])
fcasts[: start_index] = np.nan
return fcasts[:, p:]
def _ar_forecast(y, horizon, start_index, constant, arp, exogp=None, x=None):
"""
Generate mean forecasts from an AR-X model
Parameters
----------
y : ndarray
horizon : int
start_index : int
constant : float
arp : ndarray
exogp : ndarray
x : ndarray
Returns
-------
forecasts : array
"""
t = y.shape[0]
p = arp.shape[0]
fcasts = np.empty((t, p + horizon))
for i in range(p):
fcasts[p - 1:, i] = y[i:(-p + i + 1)] if i < p - 1 else y[i:]
for i in range(p, horizon + p):
fcasts[:, i] = constant + fcasts[:, i - p:i].dot(arp[::-1])
fcasts[:start_index] = np.nan
fcasts = fcasts[:, p:]
if x is not None:
exog_comp = np.dot(x, exogp[:, None])
fcasts[:-1] += exog_comp[1:]
fcasts[-1] = np.nan
fcasts[:, 1:] = np.nan
return fcasts
def harch_recursion_python(parameters, resids, sigma2, lags, nobs, backcast,
var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters
resids : ndarray
Residuals to use in the recursion
sigma2 : ndarray
Conditional variances with same shape as resids
lags : ndarray
Lag lengths in the HARCH
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : ndarray
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
"""
for t in range(nobs):
sigma2[t] = parameters[0]
for i in range(lags.shape[0]):
param = parameters[i + 1] / lags[i]
for j in range(lags[i]):
if (t - j - 1) >= 0:
sigma2[t] += param * resids[t - j - 1] * resids[t - j - 1]
else:
sigma2[t] += param * backcast
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def _ar_forecast(y, horizon, start_index, constant, arp, exogp=None, x=None):
"""
Generate mean forecasts from an AR-X model
Parameters
----------
y : ndarray
horizon : int
start_index : int
constant : float
arp : ndarray
exogp : ndarray
x : ndarray
Returns
-------
forecasts : ndarray
"""
t = y.shape[0]
p = arp.shape[0]
fcasts = np.empty((t, p + horizon))
for i in range(p):
fcasts[p - 1:, i] = y[i:(-p + i + 1)] if i < p - 1 else y[i:]
for i in range(p, horizon + p):
fcasts[:, i] = constant + fcasts[:, i - p:i].dot(arp[::-1])
fcasts[:start_index] = np.nan
fcasts = fcasts[:, p:]
if x is not None:
exog_comp = np.dot(x, exogp[:, None])
fcasts[:-1] += exog_comp[1:]
fcasts[-1] = np.nan
fcasts[:, 1:] = np.nan
return fcasts
def _ar_forecast(y, horizon, start_index, constant, arp):
"""
Parameters
----------
y : array
horizon : int
start_index : int
constant : float
arp : array
Returns
-------
forecasts : array
"""
t = y.shape[0]
p = arp.shape[0]
fcasts = np.empty((t, p + horizon))
for i in range(p):
fcasts[p - 1:, i] = y[i:(-p + i + 1)] if i < p - 1 else y[i:]
for i in range(p, horizon + p):
fcasts[:, i] = constant + fcasts[:, i - p:i].dot(arp[::-1])
fcasts[:start_index] = np.nan
return fcasts[:, p:]
def harch_recursion_python(parameters, resids, sigma2, lags, nobs, backcast,
var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters
resids : ndarray
Residuals to use in the recursion
sigma2 : ndarray
Conditional variances with same shape as resids
lags : ndarray
Lag lengths in the HARCH
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : ndarray
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
"""
for t in range(nobs):
sigma2[t] = parameters[0]
for i in range(lags.shape[0]):
param = parameters[i + 1] / lags[i]
for j in range(lags[i]):
if (t - j - 1) >= 0:
sigma2[t] += param * resids[t - j - 1] * resids[t - j - 1]
else:
sigma2[t] += param * backcast
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def arch_recursion_python(parameters, resids, sigma2, p, nobs, backcast,
var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters
resids : ndarray
Residuals to use in the recursion
sigma2 : ndarray
Conditional variances with same shape as resids
p : int
Number of lags in ARCH model
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : 2-d array
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
"""
for t in range(nobs):
sigma2[t] = parameters[0]
for i in range(p):
if (t - i - 1) < 0:
sigma2[t] += parameters[i + 1] * backcast
else:
sigma2[t] += parameters[i + 1] * resids[t - i - 1]**2
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def garch_recursion_python(parameters, fresids, sresids, sigma2, p, o, q, nobs,
backcast, var_bounds):
"""
Compute variance recursion for GARCH and related models
Parameters
----------
parameters : ndarray
Model parameters
fresids : ndarray
Absolute value of residuals raised to the power in the model. For
example, in a standard GARCH model, the power is 2.0.
sresids : ndarray
Variable containing the sign of the residuals (-1.0, 0.0, 1.0)
sigma2 : ndarray
Conditional variances with same shape as resids
p : int
Number of symmetric innovations in model
o : int
Number of asymmetric innovations in model
q : int
Number of lags of the (transformed) variance in the model
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : 2-d array
nobs by 2-element array of upper and lower bounds for conditional
transformed variances for each time period
"""
for t in range(nobs):
loc = 0
sigma2[t] = parameters[loc]
loc += 1
for j in range(p):
if (t - 1 - j) < 0:
sigma2[t] += parameters[loc] * backcast
else:
sigma2[t] += parameters[loc] * fresids[t - 1 - j]
loc += 1
for j in range(o):
if (t - 1 - j) < 0:
sigma2[t] += parameters[loc] * 0.5 * backcast
else:
sigma2[t] += parameters[loc] \
* fresids[t - 1 - j] * (sresids[t - 1 - j] < 0)
loc += 1
for j in range(q):
if (t - 1 - j) < 0:
sigma2[t] += parameters[loc] * backcast
else:
sigma2[t] += parameters[loc] * sigma2[t - 1 - j]
loc += 1
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def garch_recursion_python(parameters, fresids, sresids, sigma2, p, o, q, nobs,
backcast, var_bounds):
"""
Compute variance recursion for GARCH and related models
Parameters
----------
parameters : ndarray
Model parameters
fresids : ndarray
Absolute value of residuals raised to the power in the model. For
example, in a standard GARCH model, the power is 2.0.
sresids : ndarray
Variable containing the sign of the residuals (-1.0, 0.0, 1.0)
sigma2 : ndarray
Conditional variances with same shape as resids
p : int
Number of symmetric innovations in model
o : int
Number of asymmetric innovations in model
q : int
Number of lags of the (transformed) variance in the model
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : 2-d array
nobs by 2-element array of upper and lower bounds for conditional
transformed variances for each time period
"""
for t in range(nobs):
loc = 0
sigma2[t] = parameters[loc]
loc += 1
for j in range(p):
if (t - 1 - j) < 0:
sigma2[t] += parameters[loc] * backcast
else:
sigma2[t] += parameters[loc] * fresids[t - 1 - j]
loc += 1
for j in range(o):
if (t - 1 - j) < 0:
sigma2[t] += parameters[loc] * 0.5 * backcast
else:
sigma2[t] += parameters[loc] \
* fresids[t - 1 - j] * (sresids[t - 1 - j] < 0)
loc += 1
for j in range(q):
if (t - 1 - j) < 0:
sigma2[t] += parameters[loc] * backcast
else:
sigma2[t] += parameters[loc] * sigma2[t - 1 - j]
loc += 1
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def test_arch_multiple_lags(self):
arch = ARCH(p=5)
sv = arch.starting_values(self.resids)
assert_equal(sv.shape[0], arch.num_params)
bounds = arch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids ** 2.0)))
for i in range(1, 6):
assert_equal(bounds[i], (0.0, 1.0))
var_bounds = arch.variance_bounds(self.resids)
backcast = arch.backcast(self.resids)
parameters = np.array([0.25, 0.17, 0.16, 0.15, 0.14, 0.13])
arch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.arch_recursion(parameters, self.resids, cond_var_direct, 5,
self.T, backcast, var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
a, b = arch.constraints()
a_target = np.vstack((np.eye(6),
np.array([[0, -1.0, -1.0, -1.0, -1.0, -1.0]])))
b_target = np.array([0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1.0])
assert_array_equal(a, a_target)
assert_array_equal(b, b_target)
state = self.rng.get_state()
rng = Normal()
rng.random_state.set_state(state)
sim_data = arch.simulate(parameters, self.T, rng.simulate([]))
self.rng.set_state(state)
e = self.rng.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
for i in range(5):
if t - i - 1 < 0:
sigma2[t] += parameters[i + 1] * initial_value
else:
sigma2[t] += parameters[i + 1] * data[t - i - 1] ** 2.0
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
names = arch.parameter_names()
names_target = ['omega']
names_target.extend(['alpha[' + str(i + 1) + ']' for i in range(5)])
assert_equal(names, names_target)
assert_equal(arch.num_params, 6)
assert_equal(arch.name, 'ARCH')
def test_arch_multiple_lags(self):
arch = ARCH(p=5)
sv = arch.starting_values(self.resids)
assert_equal(sv.shape[0], arch.num_params)
bounds = arch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids ** 2.0)))
for i in range(1, 6):
assert_equal(bounds[i], (0.0, 1.0))
var_bounds = arch.variance_bounds(self.resids)
backcast = arch.backcast(self.resids)
parameters = np.array([0.25, 0.17, 0.16, 0.15, 0.14, 0.13])
arch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.arch_recursion(parameters, self.resids, cond_var_direct, 5,
self.T, backcast, var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
A, b = arch.constraints()
A_target = np.vstack((np.eye(6),
np.array([[0, -1.0, -1.0, -1.0, -1.0, -1.0]])))
b_target = np.array([0.0, 0.0, 0.0, 0.0, 0.0, 0.0, -1.0])
assert_array_equal(A, A_target)
assert_array_equal(b, b_target)
state = np.random.get_state()
rng = Normal()
sim_data = arch.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
for i in range(5):
if t - i - 1 < 0:
sigma2[t] += parameters[i + 1] * initial_value
else:
sigma2[t] += parameters[i + 1] * data[t - i - 1] ** 2.0
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
names = arch.parameter_names()
names_target = ['omega']
names_target.extend(['alpha[' + str(i + 1) + ']' for i in range(5)])
assert_equal(names, names_target)
assert_equal(arch.num_params, 6)
assert_equal(arch.name, 'ARCH')
def midas_recursion_python(parameters, weights, resids, sigma2, nobs, backcast,
var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters of the form (omega, alpha, gamma) where omega is the
intercept, alpha is the scale for all shocks and gamma is the shock
to negative returns (can be 0.0) for a symmetric model.
weights : ndarray
The weights on the lagged squared returns. Should sum to 1
resids : ndarray
Residuals to use in the recursion
sigma2 : ndarray
Conditional variances with same shape as resids
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : ndarray
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
"""
omega, alpha, gamma = parameters
m = weights.shape[0]
aw = np.zeros(m)
gw = np.zeros(m)
for i in range(m):
aw[i] = alpha * weights[i]
gw[i] = gamma * weights[i]
resids2 = np.zeros(nobs)
for t in range(nobs):
resids2[t] = resids[t] * resids[t]
sigma2[t] = omega
for i in range(m):
if (t - i - 1) >= 0:
sigma2[t] += (aw[i] + gw[i] *
(resids[t - i - 1] < 0)) * resids2[t - i - 1]
else:
sigma2[t] += (aw[i] + 0.5 * gw[i]) * backcast
if sigma2[t] < var_bounds[t, 0]:
sigma2[t] = var_bounds[t, 0]
elif sigma2[t] > var_bounds[t, 1]:
if np.isinf(sigma2[t]):
sigma2[t] = var_bounds[t, 1] + 1000
else:
sigma2[t] = var_bounds[t, 1] + np.log(
sigma2[t] / var_bounds[t, 1])
return sigma2
def midas_recursion_python(parameters, weights, resids, sigma2, nobs, backcast, var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters of the form (omega, alpha, gamma) where omega is the
intercept, alpha is the scale for all shocks and gamma is the shock
to negative returns (can be 0.0) for a symmetric model.
weights : ndarray
The weights on the lagged squared returns. Should sum to 1
resids : ndarray
Residuals to use in the recursion
sigma2 : ndarray
Conditional variances with same shape as resids
nobs : int
Length of resids
backcast : float
Value to use when initializing the recursion
var_bounds : ndarray
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
"""
omega, alpha, gamma = parameters
m = weights.shape[0]
aw = np.zeros(m)
gw = np.zeros(m)
for i in range(m):
aw[i] = alpha * weights[i]
gw[i] = gamma * weights[i]
resids2 = np.zeros(nobs)
for t in range(nobs):
resids2[t] = resids[t] * resids[t]
sigma2[t] = omega
for i in range(m):
if (t - i - 1) >= 0:
sigma2[t] += (aw[i] + gw[i] * (resids[t - i - 1] < 0)) * resids2[t - i - 1]
else:
sigma2[t] += (aw[i] + 0.5 * gw[i]) * backcast
if sigma2[t] < var_bounds[t, 0]:
sigma2[t] = var_bounds[t, 0]
elif sigma2[t] > var_bounds[t, 1]:
if np.isinf(sigma2[t]):
sigma2[t] = var_bounds[t, 1] + 1000
else:
sigma2[t] = var_bounds[t, 1] + np.log(sigma2[t] / var_bounds[t, 1])
return sigma2
def figarch_recursion_python(parameters, fresids, sigma2, p, q, nobs, trunc_lag, backcast,
var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters of the form (omega, phi, d, beta) where omega is the
intercept, d is the fractional integration coefficient and phi and beta
are parameters of the volatility process.
fresids : ndarray
Absolute value of residuals raised to the power in the model. For
example, in a standard GARCH model, the power is 2.0.
sigma2 : ndarray
Conditional variances with same shape as resids
p : int
0 or 1 to indicate whether the model contains phi
q : int
0 or 1 to indicate whether the model contains beta
nobs : int
Length of resids
trunc_lag : int
Truncation lag for the ARCH approximations
backcast : float
Value to use when initializing the recursion
var_bounds : ndarray
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
Returns
-------
sigma2 : ndarray
Conditional variances
"""
omega = parameters[0]
beta = parameters[1 + p + q] if q else 0.0
omega_tilde = omega / (1-beta)
lam = figarch_weights(parameters[1:], p, q, trunc_lag)
for t in range(nobs):
bc_weight = 0.0
for i in range(t, trunc_lag):
bc_weight += lam[i]
sigma2[t] = omega_tilde + bc_weight * backcast
for i in range(min(t, trunc_lag)):
sigma2[t] += lam[i] * fresids[t - i - 1]
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def figarch_recursion_python(parameters, fresids, sigma2, p, q, nobs,
trunc_lag, backcast, var_bounds):
"""
Parameters
----------
parameters : ndarray
Model parameters of the form (omega, phi, d, beta) where omega is the
intercept, d is the fractional integration coefficient and phi and beta
are parameters of the volatility process.
fresids : ndarray
Absolute value of residuals raised to the power in the model. For
example, in a standard GARCH model, the power is 2.0.
sigma2 : ndarray
Conditional variances with same shape as resids
p : int
0 or 1 to indicate whether the model contains phi
q : int
0 or 1 to indicate whether the model contains beta
nobs : int
Length of resids
trunc_lag : int
Truncation lag for the ARCH approximations
backcast : float
Value to use when initializing the recursion
var_bounds : ndarray
nobs by 2-element array of upper and lower bounds for conditional
variances for each time period
Returns
-------
sigma2 : ndarray
Conditional variances
"""
omega = parameters[0]
beta = parameters[1 + p + q] if q else 0.0
omega_tilde = omega / (1 - beta)
lam = figarch_weights(parameters[1:], p, q, trunc_lag)
for t in range(nobs):
bc_weight = 0.0
for i in range(t, trunc_lag):
bc_weight += lam[i]
sigma2[t] = omega_tilde + bc_weight * backcast
for i in range(min(t, trunc_lag)):
sigma2[t] += lam[i] * fresids[t - i - 1]
sigma2[t] = bounds_check(sigma2[t], var_bounds[t])
return sigma2
def test_arch_lm(simulated_data):
zm = ZeroMean(simulated_data, volatility=GARCH())
res = zm.fit(disp=DISPLAY)
wald = res.arch_lm_test()
nobs = simulated_data.shape[0]
df = int(np.ceil(12. * np.power(nobs / 100., 1 / 4.)))
assert wald.df == df
assert 'Standardized' not in wald.null
assert 'Standardized' not in wald.alternative
assert 'H0: Standardized' not in wald.__repr__()
assert 'heteroskedastic' in wald.__repr__()
resids2 = res.resid**2
data = [resids2.shift(i) for i in range(df + 1)]
data = pd.concat(data, 1).dropna()
lhs = data.iloc[:, 0]
rhs = smtools.add_constant(data.iloc[:, 1:])
ols_res = smlm.OLS(lhs, rhs).fit()
assert_almost_equal(wald.stat, nobs * ols_res.rsquared)
assert len(wald.critical_values) == 3
assert '10%' in wald.critical_values
wald = res.arch_lm_test(lags=5)
assert wald.df == 5
assert_almost_equal(wald.pval, 1 - stats.chi2(5).cdf(wald.stat))
wald = res.arch_lm_test(standardized=True)
assert wald.df == df
assert 'Standardized' in wald.null
assert 'Standardized' in wald.alternative
assert_almost_equal(wald.pval, 1 - stats.chi2(df).cdf(wald.stat))
assert 'H0: Standardized' in wald.__repr__()
def test_garch_no_symmetric(self):
garch = GARCH(p=0, o=1, q=1)
sv = garch.starting_values(self.resids)
assert_equal(sv.shape[0], garch.num_params)
bounds = garch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids ** 2.0)))
assert_equal(bounds[1], (0.0, 2.0))
assert_equal(bounds[2], (0.0, 1.0))
var_bounds = garch.variance_bounds(self.resids)
backcast = garch.backcast(self.resids)
parameters = np.array([.1, .1, .8])
names = garch.parameter_names()
names_target = ['omega', 'gamma[1]', 'beta[1]']
assert_equal(names, names_target)
garch.compute_variance(parameters, self.resids, self.sigma2,
backcast, var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.garch_recursion(parameters,
self.resids ** 2.0,
np.sign(self.resids),
cond_var_direct,
0, 1, 1, self.T, backcast, var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
a, b = garch.constraints()
a_target = np.vstack((np.eye(3), np.array([[0, -0.5, -1.0]])))
b_target = np.array([0.0, 0.0, 0.0, -1.0])
assert_array_equal(a, a_target)
assert_array_equal(b, b_target)
state = self.rng.get_state()
rng = Normal()
rng.random_state.set_state(state)
sim_data = garch.simulate(parameters, self.T, rng.simulate([]))
self.rng.set_state(state)
e = self.rng.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
shock = 0.5 * initial_value if t == 0 else \
data[t - 1] ** 2.0 * (data[t - 1] < 0)
sigma2[t] += parameters[1] * shock
lagged_value = initial_value if t == 0 else sigma2[t - 1]
sigma2[t] += parameters[2] * lagged_value
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
assert_equal(garch.p, 0)
assert_equal(garch.o, 1)
assert_equal(garch.q, 1)
assert_equal(garch.num_params, 3)
assert_equal(garch.name, 'GJR-GARCH')
def test_constant_mean(self):
cm = ConstantMean(self.y)
parameters = np.array([5.0, 1.0])
cm.simulate(parameters, self.T)
assert_equal(cm.num_params, 1)
bounds = cm.bounds()
assert_equal(bounds, [(-np.inf, np.inf)])
assert_equal(cm.constant, True)
a, b = cm.constraints()
assert_equal(a, np.empty((0, 1)))
assert_equal(b, np.empty((0, )))
assert_true(isinstance(cm.volatility, ConstantVariance))
assert_true(isinstance(cm.distribution, Normal))
assert_equal(cm.first_obs, 0)
assert_equal(cm.last_obs, 1000)
assert_equal(cm.lags, None)
res = cm.fit()
assert_almost_equal(res.params, np.array([self.y.mean(),
self.y.var()]))
forecasts = res.forecast(horizon=20, start=20)
direct = pd.DataFrame(
index=np.arange(self.y.shape[0]),
columns=['h.{0:>02d}'.format(i + 1) for i in range(20)],
dtype=np.float64)
direct.iloc[20:, :] = res.params.iloc[0]
assert_frame_equal(direct, forecasts)
def test_ewma(self):
ewma = EWMAVariance()
sv = ewma.starting_values(self.resids)
assert_equal(sv.shape[0], ewma.num_params)
bounds = ewma.bounds(self.resids)
assert_equal(len(bounds), 0)
var_bounds = ewma.variance_bounds(self.resids)
backcast = ewma.backcast(self.resids)
parameters = np.array([])
names = ewma.parameter_names()
names_target = []
assert_equal(names, names_target)
ewma.compute_variance(parameters, self.resids, self.sigma2,
backcast, var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
parameters = np.array([0.0, 0.06, 0.94])
rec.garch_recursion(parameters,
self.resids ** 2.0,
np.sign(self.resids),
cond_var_direct,
1, 0, 1, self.T, backcast, var_bounds)
assert_allclose(self.sigma2 / cond_var_direct,
np.ones_like(self.sigma2))
a, b = ewma.constraints()
a_target = np.empty((0, 0))
b_target = np.empty((0,))
assert_array_equal(a, a_target)
assert_array_equal(b, b_target)
state = self.rng.get_state()
rng = Normal()
rng.random_state.set_state(state)
sim_data = ewma.simulate(parameters, self.T, rng.simulate([]))
self.rng.set_state(state)
e = self.rng.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
sigma2[0] = initial_value
data[0] = np.sqrt(initial_value)
for t in range(1, self.T + 500):
sigma2[t] = 0.94 * sigma2[t - 1] + 0.06 * data[t - 1] ** 2.0
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
assert_equal(ewma.num_params, 0)
assert_equal(ewma.name, 'EWMA/RiskMetrics')
assert isinstance(ewma.__str__(), str)
txt = ewma.__repr__()
assert str(hex(id(ewma))) in txt
def figarch_weights_python(parameters, p, q, truncation):
r"""
Parameters
----------
parameters : ndarray
Model parameters of the form (omega, phi, d, beta) where omega is the
intercept, d is the fractional integration coefficient and phi and beta
are parameters of the volatility process.
p : int
0 or 1 to indicate whether the model contains phi
q : int
0 or 1 to indicate whether the model contains beta
trunc_lag : int
Truncation lag for the ARCH approximations
Returns
-------
lam : ndarray
ARCH(:math:`\infty`) coefficients used to approximate model dynamics
"""
phi = parameters[0] if p else 0.0
d = parameters[1] if p else parameters[0]
beta = parameters[p + q] if q else 0.0
# Recursive weight computation
lam = np.empty(truncation)
delta = np.empty(truncation)
lam[0] = phi - beta + d
delta[0] = d
for i in range(1, truncation):
delta[i] = (i - d) / (i + 1) * delta[i - 1]
lam[i] = beta * lam[i - 1] + (delta[i] - phi * delta[i - 1])
return lam
def cgarch_recursion_python(parameters, fresids, sigma2, backcast, var_bounds,
g2, q2):
sqrd_resids = fresids
nobs = len(sqrd_resids)
alpha, beta, omega, raw, phi = parameters
initial_sigma2 = backcast
initial_q2 = 0.05
initial_g2 = initial_sigma2 - initial_q2
# g is short term variance and q is the long term one
g2[0] = initial_g2
q2[0] = initial_q2
sigma2[0] = initial_sigma2
for t in range(1, nobs):
g2[t] = alpha * (sqrd_resids[t - 1] - q2[t - 1]) + beta * g2[t - 1]
q2[t] = omega + raw * q2[t - 1] + phi * (sqrd_resids[t - 1] -
sigma2[t - 1])
sigma2[t] = g2[t] + q2[t]
if sigma2[t] < var_bounds[t, 0]:
sigma2[t] = var_bounds[t, 0]
elif sigma2[t] > var_bounds[t, 1]:
if not np.isinf(sigma2[t]):
sigma2[t] = var_bounds[t, 1] + log(
sigma2[t] / var_bounds[t, 1])
else:
sigma2[t] = var_bounds[t, 1] + 1000
return sigma2
def test_ewma(self):
ewma = EWMAVariance()
sv = ewma.starting_values(self.resids)
assert_equal(sv.shape[0], ewma.num_params)
bounds = ewma.bounds(self.resids)
assert_equal(len(bounds), 0)
var_bounds = ewma.variance_bounds(self.resids)
backcast = ewma.backcast(self.resids)
parameters = np.array([])
names = ewma.parameter_names()
names_target = []
assert_equal(names, names_target)
ewma.compute_variance(parameters, self.resids, self.sigma2,
backcast, var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
parameters = np.array([0.0, 0.06, 0.94])
rec.garch_recursion(parameters,
self.resids ** 2.0,
np.sign(self.resids),
cond_var_direct,
1, 0, 1, self.T, backcast, var_bounds)
# sigma3 = np.zeros_like(self.sigma2)
# sigma3[0] = backcast
# for t in range(1,self.T):
# sigma3[t] = 0.94 * sigma3[t-1] + 0.06 * self.resids[t-1]**2.0
assert_allclose(self.sigma2 / cond_var_direct,
np.ones_like(self.sigma2))
A, b = ewma.constraints()
A_target = np.empty((0, 0))
b_target = np.empty((0,))
assert_array_equal(A, A_target)
assert_array_equal(b, b_target)
state = np.random.get_state()
rng = Normal()
sim_data = ewma.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
sigma2[0] = initial_value
data[0] = np.sqrt(initial_value)
for t in range(1, self.T + 500):
sigma2[t] = 0.94 * sigma2[t - 1] + 0.06 * data[t - 1] ** 2.0
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
assert_equal(ewma.num_params, 0)
assert_equal(ewma.name, 'EWMA/RiskMetrics')
def test_figarch_recursion(self):
nobs, resids, = self.nobs, self.resids
sigma2, backcast = self.sigma2, self.backcast
parameters = np.array([1.0, 0.2, 0.4, 0.3])
fresids = resids**2
p = q = 1
trunc_lag = 1000
rec.figarch_recursion(parameters, fresids, sigma2, p, q, nobs,
trunc_lag, backcast, self.var_bounds)
lam = rec.figarch_weights(parameters[1:], p, q, truncation=trunc_lag)
lam_rev = lam[::-1]
omega_tilde = parameters[0] / (1 - parameters[-1])
sigma2_direct = np.empty_like(sigma2)
for t in range(nobs):
backcasts = trunc_lag - t
sigma2_direct[t] = omega_tilde
if backcasts:
sigma2_direct[t] += backcast * lam_rev[:backcasts].sum()
if t:
sigma2_direct[t] += np.sum(lam_rev[-t:] *
fresids[max(0, t - 1000):t])
assert_almost_equal(sigma2_direct, sigma2)
recpy.figarch_recursion(parameters, fresids, sigma2, p, q, nobs,
trunc_lag, backcast, self.var_bounds)
sigma2_numba = sigma2.copy()
recpy.figarch_recursion_python(parameters, fresids, sigma2, p, q, nobs,
trunc_lag, backcast, self.var_bounds)
sigma2_python = sigma2.copy()
rec.figarch_recursion(parameters, fresids, sigma2, p, q, nobs,
trunc_lag, backcast, self.var_bounds)
assert_almost_equal(sigma2_numba, sigma2)
assert_almost_equal(sigma2_python, sigma2)
def test_constant_mean(self):
cm = ConstantMean(self.y)
parameters = np.array([5.0, 1.0])
cm.simulate(parameters, self.T)
assert_equal(cm.num_params, 1)
bounds = cm.bounds()
assert_equal(bounds, [(-np.inf, np.inf)])
assert_equal(cm.constant, True)
a, b = cm.constraints()
assert_equal(a, np.empty((0, 1)))
assert_equal(b, np.empty((0,)))
assert isinstance(cm.volatility, ConstantVariance)
assert isinstance(cm.distribution, Normal)
assert_equal(cm.lags, None)
res = cm.fit(disp='off')
expected = np.array([self.y.mean(), self.y.var()])
assert_almost_equal(res.params, expected)
forecasts = res.forecast(horizon=20, start=20)
direct = pd.DataFrame(index=np.arange(self.y.shape[0]),
columns=['h.{0:>02d}'.format(i + 1) for i in
range(20)],
dtype=np.float64)
direct.iloc[20:, :] = res.params.iloc[0]
# TODO
# assert_frame_equal(direct, forecasts)
assert isinstance(forecasts, ARCHModelForecast)
def figarch_weights_python(parameters, p, q, truncation):
r"""
Parameters
----------
parameters : ndarray
Model parameters of the form (omega, phi, d, beta) where omega is the
intercept, d is the fractional integration coefficient and phi and beta
are parameters of the volatility process.
p : int
0 or 1 to indicate whether the model contains phi
q : int
0 or 1 to indicate whether the model contains beta
trunc_lag : int
Truncation lag for the ARCH approximations
Returns
-------
lam : ndarray
ARCH(:math:`\infty`) coefficients used to approximate model dynamics
"""
phi = parameters[0] if p else 0.0
d = parameters[1] if p else parameters[0]
beta = parameters[p + q] if q else 0.0
# Recursive weight computation
lam = np.empty(truncation)
delta = np.empty(truncation)
lam[0] = phi - beta + d
delta[0] = d
for i in range(1, truncation):
delta[i] = (i - d) / (i + 1) * delta[i - 1]
lam[i] = beta * lam[i - 1] + (delta[i] - phi * delta[i - 1])
return lam
def test_constant_mean(self):
cm = ConstantMean(self.y)
parameters = np.array([5.0, 1.0])
cm.simulate(parameters, self.T)
assert_equal(cm.num_params, 1)
with pytest.raises(ValueError):
cm.simulate(parameters, self.T, x=np.array(10))
bounds = cm.bounds()
assert_equal(bounds, [(-np.inf, np.inf)])
assert_equal(cm.constant, True)
a, b = cm.constraints()
assert_equal(a, np.empty((0, 1)))
assert_equal(b, np.empty((0,)))
assert isinstance(cm.volatility, ConstantVariance)
assert isinstance(cm.distribution, Normal)
assert_equal(cm.lags, None)
res = cm.fit(disp='off')
expected = np.array([self.y.mean(), self.y.var()])
assert_almost_equal(res.params, expected)
forecasts = res.forecast(horizon=20, start=20)
direct = pd.DataFrame(index=np.arange(self.y.shape[0]),
columns=['h.{0:>02d}'.format(i + 1) for i in
range(20)],
dtype=np.float64)
direct.iloc[20:, :] = res.params.iloc[0]
# TODO
# assert_frame_equal(direct, forecasts)
assert isinstance(forecasts, ARCHModelForecast)
assert isinstance(cm.__repr__(), str)
assert isinstance(cm.__str__(), str)
assert '<strong>' in cm._repr_html_()
def test_figarch_recursion(self):
nobs, resids, = self.nobs, self.resids
sigma2, backcast = self.sigma2, self.backcast
parameters = np.array([1.0, 0.2, 0.4, 0.3])
fresids = resids ** 2
p = q = 1
trunc_lag = 1000
rec.figarch_recursion(parameters, fresids, sigma2, p, q, nobs, trunc_lag, backcast,
self.var_bounds)
lam = rec.figarch_weights(parameters[1:], p, q, truncation=trunc_lag)
lam_rev = lam[::-1]
omega_tilde = parameters[0] / (1 - parameters[-1])
sigma2_direct = np.empty_like(sigma2)
for t in range(nobs):
backcasts = trunc_lag - t
sigma2_direct[t] = omega_tilde
if backcasts:
sigma2_direct[t] += backcast * lam_rev[:backcasts].sum()
if t:
sigma2_direct[t] += np.sum(lam_rev[-t:] * fresids[max(0, t - 1000):t])
assert_almost_equal(sigma2_direct, sigma2)
recpy.figarch_recursion(parameters, fresids, sigma2, p, q, nobs, trunc_lag, backcast,
self.var_bounds)
sigma2_numba = sigma2.copy()
recpy.figarch_recursion_python(parameters, fresids, sigma2, p, q, nobs, trunc_lag,
backcast, self.var_bounds)
sigma2_python = sigma2.copy()
rec.figarch_recursion(parameters, fresids, sigma2, p, q, nobs, trunc_lag, backcast,
self.var_bounds)
assert_almost_equal(sigma2_numba, sigma2)
assert_almost_equal(sigma2_python, sigma2)
def test_zero_mean(self):
zm = ZeroMean(self.y)
parameters = np.array([1.0])
data = zm.simulate(parameters, self.T)
assert_equal(data.shape, (self.T, 3))
assert_equal(data['data'].shape[0], self.T)
assert_equal(zm.num_params, 0)
bounds = zm.bounds()
assert_equal(bounds, [])
assert_equal(zm.constant, False)
a, b = zm.constraints()
assert_equal(a, np.empty((0, 0)))
assert_equal(b, np.empty((0,)))
assert isinstance(zm.volatility, ConstantVariance)
assert isinstance(zm.distribution, Normal)
assert_equal(zm.lags, None)
res = zm.fit(disp='off')
assert_almost_equal(res.params, np.array([np.mean(self.y ** 2)]))
forecasts = res.forecast(horizon=99)
direct = pd.DataFrame(index=np.arange(self.y.shape[0]),
columns=['h.{0:>02d}'.format(i + 1) for i in
range(99)],
dtype=np.float64)
direct.iloc[:, :] = 0.0
assert isinstance(forecasts, ARCHModelForecast)
# TODO
# assert_frame_equal(direct, forecasts)
garch = GARCH()
zm.volatility = garch
zm.fit(update_freq=0, disp=DISPLAY)
def test_zero_mean(self):
zm = ZeroMean(self.y)
parameters = np.array([1.0])
data = zm.simulate(parameters, self.T)
assert_equal(data.shape, (self.T, 3))
assert_equal(data['data'].shape[0], self.T)
assert_equal(zm.num_params, 0)
bounds = zm.bounds()
assert_equal(bounds, [])
assert_equal(zm.constant, False)
a, b = zm.constraints()
assert_equal(a, np.empty((0, 0)))
assert_equal(b, np.empty((0,)))
assert isinstance(zm.volatility, ConstantVariance)
assert isinstance(zm.distribution, Normal)
assert_equal(zm.lags, None)
res = zm.fit(disp='off')
assert_almost_equal(res.params, np.array([np.mean(self.y ** 2)]))
forecasts = res.forecast(horizon=99)
direct = pd.DataFrame(index=np.arange(self.y.shape[0]),
columns=['h.{0:>02d}'.format(i + 1) for i in
range(99)],
dtype=np.float64)
direct.iloc[:, :] = 0.0
assert isinstance(forecasts, ARCHModelForecast)
# TODO
# assert_frame_equal(direct, forecasts)
garch = GARCH()
zm.volatility = garch
zm.fit(update_freq=0, disp=DISPLAY)
assert isinstance(zm.__repr__(), str)
assert isinstance(zm.__str__(), str)
assert '<strong>' in zm._repr_html_()
def test_garch(self):
garch = GARCH()
sv = garch.starting_values(self.resids)
assert_equal(sv.shape[0], garch.num_params)
bounds = garch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids**2.0)))
assert_equal(bounds[1], (0.0, 1.0))
assert_equal(bounds[2], (0.0, 1.0))
backcast = garch.backcast(self.resids)
w = 0.94**np.arange(75)
assert_almost_equal(backcast,
np.sum((self.resids[:75]**2) * (w / w.sum())))
var_bounds = garch.variance_bounds(self.resids)
parameters = np.array([.1, .1, .8])
garch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.garch_recursion(parameters, self.resids**2.0, np.sign(self.resids),
cond_var_direct, 1, 0, 1, self.T, backcast,
var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
A, b = garch.constraints()
A_target = np.vstack((np.eye(3), np.array([[0, -1.0, -1.0]])))
b_target = np.array([0.0, 0.0, 0.0, -1.0])
assert_array_equal(A, A_target)
assert_array_equal(b, b_target)
state = np.random.get_state()
rng = Normal()
sim_data = garch.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
shock = initial_value if t == 0 else data[t - 1]**2.0
sigma2[t] += parameters[1] * shock
lagged_value = initial_value if t == 0 else sigma2[t - 1]
sigma2[t] += parameters[2] * lagged_value
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data / sim_data[0], np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
names = garch.parameter_names()
names_target = ['omega', 'alpha[1]', 'beta[1]']
assert_equal(names, names_target)
assert_equal(garch.name, 'GARCH')
assert_equal(garch.num_params, 3)
assert_equal(garch.power, 2.0)
assert_equal(garch.p, 1)
assert_equal(garch.o, 0)
assert_equal(garch.q, 1)
def test_egarch(self):
nobs = self.nobs
parameters = np.array([0.0, 0.1, -0.1, 0.95])
resids, sigma2 = self.resids, self.sigma2
p = o = q = 1
backcast = 0.0
var_bounds = self.var_bounds
lnsigma2 = np.empty_like(sigma2)
std_resids = np.empty_like(sigma2)
abs_std_resids = np.empty_like(sigma2)
recpy.egarch_recursion(parameters, resids, sigma2, p, o, q, nobs,
backcast, var_bounds, lnsigma2, std_resids,
abs_std_resids)
sigma2_numba = sigma2.copy()
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
sigma2_python = sigma2.copy()
rec.egarch_recursion(parameters, resids, sigma2, p, o, q, nobs,
backcast, var_bounds, lnsigma2, std_resids,
abs_std_resids)
assert_almost_equal(sigma2_numba, sigma2)
assert_almost_equal(sigma2_python, sigma2)
norm_const = np.sqrt(2 / np.pi)
for t in range(nobs):
lnsigma2[t] = parameters[0]
if t == 0:
lnsigma2[t] += parameters[3] * backcast
else:
stdresid = resids[t - 1] / np.sqrt(sigma2[t - 1])
lnsigma2[t] += parameters[1] * (np.abs(stdresid) - norm_const)
lnsigma2[t] += parameters[2] * stdresid
lnsigma2[t] += parameters[3] * lnsigma2[t - 1]
sigma2[t] = np.exp(lnsigma2[t])
assert_almost_equal(sigma2_python, sigma2)
parameters = np.array([-100.0, 0.1, -0.1, 0.95])
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
assert np.all(sigma2 >= self.var_bounds[:, 0])
assert np.all(sigma2 <= 2 * self.var_bounds[:, 1])
parameters = np.array([0.0, 0.1, -0.1, 9.5])
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
assert np.all(sigma2 >= self.var_bounds[:, 0])
assert np.all(sigma2 <= 2 * self.var_bounds[:, 1])
parameters = np.array([0.0, 0.1, -0.1, 0.95])
mod_resids = resids.copy()
mod_resids[:1] = np.inf
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
assert np.all(sigma2 >= self.var_bounds[:, 0])
assert np.all(sigma2 <= 2 * self.var_bounds[:, 1])
def test_egarch(self):
nobs = self.nobs
parameters = np.array([0.0, 0.1, -0.1, 0.95])
resids, sigma2 = self.resids, self.sigma2
p = o = q = 1
backcast = 0.0
var_bounds = self.var_bounds
lnsigma2 = np.empty_like(sigma2)
std_resids = np.empty_like(sigma2)
abs_std_resids = np.empty_like(sigma2)
recpy.egarch_recursion(parameters, resids, sigma2, p, o, q, nobs,
backcast, var_bounds, lnsigma2, std_resids,
abs_std_resids)
sigma2_numba = sigma2.copy()
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
sigma2_python = sigma2.copy()
rec.egarch_recursion(parameters, resids, sigma2, p, o, q, nobs,
backcast, var_bounds, lnsigma2, std_resids,
abs_std_resids)
assert_almost_equal(sigma2_numba, sigma2)
assert_almost_equal(sigma2_python, sigma2)
norm_const = np.sqrt(2 / np.pi)
for t in range(nobs):
lnsigma2[t] = parameters[0]
if t == 0:
lnsigma2[t] += parameters[3] * backcast
else:
stdresid = resids[t - 1] / np.sqrt(sigma2[t - 1])
lnsigma2[t] += parameters[1] * (np.abs(stdresid) - norm_const)
lnsigma2[t] += parameters[2] * stdresid
lnsigma2[t] += parameters[3] * lnsigma2[t - 1]
sigma2[t] = np.exp(lnsigma2[t])
assert_almost_equal(sigma2_python, sigma2)
parameters = np.array([-100.0, 0.1, -0.1, 0.95])
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
assert np.all(sigma2 >= self.var_bounds[:, 0])
assert np.all(sigma2 <= 2 * self.var_bounds[:, 1])
parameters = np.array([0.0, 0.1, -0.1, 9.5])
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
assert np.all(sigma2 >= self.var_bounds[:, 0])
assert np.all(sigma2 <= 2 * self.var_bounds[:, 1])
parameters = np.array([0.0, 0.1, -0.1, 0.95])
mod_resids = resids.copy()
mod_resids[:1] = np.inf
recpy.egarch_recursion_python(parameters, resids, sigma2, p, o, q,
nobs, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
assert np.all(sigma2 >= self.var_bounds[:, 0])
assert np.all(sigma2 <= 2 * self.var_bounds[:, 1])
def test_garch_no_symmetric(self):
garch = GARCH(p=0, o=1, q=1)
sv = garch.starting_values(self.resids)
assert_equal(sv.shape[0], garch.num_params)
bounds = garch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids ** 2.0)))
assert_equal(bounds[1], (0.0, 2.0))
assert_equal(bounds[2], (0.0, 1.0))
var_bounds = garch.variance_bounds(self.resids)
backcast = garch.backcast(self.resids)
parameters = np.array([.1, .1, .8])
names = garch.parameter_names()
names_target = ['omega', 'gamma[1]', 'beta[1]']
assert_equal(names, names_target)
garch.compute_variance(parameters, self.resids, self.sigma2,
backcast, var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.garch_recursion(parameters,
self.resids ** 2.0,
np.sign(self.resids),
cond_var_direct,
0, 1, 1, self.T, backcast, var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
A, b = garch.constraints()
A_target = np.vstack((np.eye(3), np.array([[0, -0.5, -1.0]])))
b_target = np.array([0.0, 0.0, 0.0, -1.0])
assert_array_equal(A, A_target)
assert_array_equal(b, b_target)
state = np.random.get_state()
rng = Normal()
sim_data = garch.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
shock = 0.5 * initial_value if t == 0 else \
data[t - 1] ** 2.0 * (data[t - 1] < 0)
sigma2[t] += parameters[1] * shock
lagged_value = initial_value if t == 0 else sigma2[t - 1]
sigma2[t] += parameters[2] * lagged_value
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
assert_equal(garch.p, 0)
assert_equal(garch.o, 1)
assert_equal(garch.q, 1)
assert_equal(garch.num_params, 3)
assert_equal(garch.name, 'GJR-GARCH')
def test_figarch_weights(self):
parameters = np.array([1.0, 0.4])
lam = rec.figarch_weights(parameters[1:], 0, 0, truncation=1000)
lam_direct = np.empty_like(lam)
lam_direct[0] = parameters[-1]
for i in range(1, 1000):
lam_direct[i] = (i - parameters[-1]) / (i + 1) * lam_direct[i - 1]
assert_almost_equal(lam, lam_direct)
def test_figarch_weights(self):
parameters = np.array([1.0, 0.4])
lam = rec.figarch_weights(parameters[1:], 0, 0, truncation=1000)
lam_direct = np.empty_like(lam)
lam_direct[0] = parameters[-1]
for i in range(1, 1000):
lam_direct[i] = (i - parameters[-1]) / (i + 1) * lam_direct[i - 1]
assert_almost_equal(lam, lam_direct)
def test_arch(self):
arch = ARCH()
sv = arch.starting_values(self.resids)
assert_equal(sv.shape[0], arch.num_params)
bounds = arch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids ** 2.0)))
assert_equal(bounds[1], (0.0, 1.0))
backcast = arch.backcast(self.resids)
w = 0.94 ** np.arange(75)
assert_almost_equal(backcast,
np.sum((self.resids[:75] ** 2) * (w / w.sum())))
parameters = np.array([0.5, 0.7])
var_bounds = arch.variance_bounds(self.resids)
arch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.arch_recursion(parameters, self.resids, cond_var_direct, 1,
self.T, backcast, var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
a, b = arch.constraints()
a_target = np.vstack((np.eye(2), np.array([[0, -1.0]])))
b_target = np.array([0.0, 0.0, -1.0])
assert_array_equal(a, a_target)
assert_array_equal(b, b_target)
state = self.rng.get_state()
rng = Normal()
rng.random_state.set_state(state)
sim_data = arch.simulate(parameters, self.T, rng.simulate([]))
self.rng.set_state(state)
e = self.rng.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
shock = initial_value if t == 0 else data[t - 1] ** 2.0
sigma2[t] += parameters[1] * shock
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
names = arch.parameter_names()
names_target = ['omega', 'alpha[1]']
assert_equal(names, names_target)
assert_equal(arch.name, 'ARCH')
assert_equal(arch.num_params, 2)
assert_equal(arch.p, 1)
assert isinstance(arch.__str__(), str)
txt = arch.__repr__()
assert str(hex(id(arch))) in txt
def test_arch(self):
arch = ARCH()
sv = arch.starting_values(self.resids)
assert_equal(sv.shape[0], arch.num_params)
bounds = arch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids ** 2.0)))
assert_equal(bounds[1], (0.0, 1.0))
backcast = arch.backcast(self.resids)
w = 0.94 ** np.arange(75)
assert_almost_equal(backcast,
np.sum((self.resids[:75] ** 2) * (w / w.sum())))
parameters = np.array([0.5, 0.7])
var_bounds = arch.variance_bounds(self.resids)
arch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.arch_recursion(parameters, self.resids, cond_var_direct, 1,
self.T, backcast, var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
A, b = arch.constraints()
A_target = np.vstack((np.eye(2), np.array([[0, -1.0]])))
b_target = np.array([0.0, 0.0, -1.0])
assert_array_equal(A, A_target)
assert_array_equal(b, b_target)
state = np.random.get_state()
rng = Normal()
sim_data = arch.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
shock = initial_value if t == 0 else data[t - 1] ** 2.0
sigma2[t] += parameters[1] * shock
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
names = arch.parameter_names()
names_target = ['omega', 'alpha[1]']
assert_equal(names, names_target)
assert_equal(arch.name, 'ARCH')
assert_equal(arch.num_params, 2)
assert_equal(arch.p, 1)
assert_true(isinstance(arch.__str__(), str))
repr = arch.__repr__()
assert_true(str(hex(id(arch))) in repr)
def _compute_statistic(self):
overlap, debiased, robust = self._overlap, self._debiased, self._robust
y, nobs, q, trend = self._y, self._nobs, self._lags, self._trend
nq = nobs - 1
if not overlap:
# Check length of y
if nq % q != 0:
extra = nq % q
y = y[:-extra]
warnings.warn(
invalid_length_doc.format(var='y', block=q, drop=extra),
InvalidLengthWarning)
nobs = y.shape[0]
if trend == 'nc':
mu = 0
else:
mu = (y[-1] - y[0]) / (nobs - 1)
delta_y = diff(y)
nq = delta_y.shape[0]
sigma2_1 = sum((delta_y - mu)**2.0) / nq
if not overlap:
delta_y_q = y[q::q] - y[0:-q:q]
sigma2_q = sum((delta_y_q - q * mu)**2.0) / nq
self._summary_text = ['Computed with non-overlapping blocks']
else:
delta_y_q = y[q:] - y[:-q]
sigma2_q = sum((delta_y_q - q * mu)**2.0) / (nq * q)
self._summary_text = ['Computed with overlapping blocks']
if debiased and overlap:
sigma2_1 *= nq / (nq - 1)
m = q * (nq - q + 1) * (1 - (q / nq))
sigma2_q *= (nq * q) / m
self._summary_text = [
'Computed with overlapping blocks '
'(de-biased)'
]
if not overlap:
self._stat_variance = 2.0 * (q - 1)
elif not robust:
self._stat_variance = (2 * (2 * q - 1) * (q - 1)) / (2 * q)
else:
z2 = (delta_y - mu)**2.0
scale = sum(z2)**2.0
theta = 0.0
for k in range(1, q):
delta = nq * z2[k:].dot(z2[:-k]) / scale
theta += (1 - k / q)**2.0 * delta
self._stat_variance = theta
self._vr = sigma2_q / sigma2_1
self._stat = sqrt(nq) * (self._vr - 1) / sqrt(self._stat_variance)
self._pvalue = 2 - 2 * norm.cdf(abs(self._stat))
def _generate_lag_names(self):
lags = self._lags
names = []
var_name = self._y_series.name
if len(var_name) > 10:
var_name = var_name[:4] + '...' + var_name[-3:]
for i in range(lags.shape[1]):
names.append(var_name + '[' + str(lags[1, i]) + ']')
return names
def test_align(self):
dates = pd.date_range('2000-01-01', '2010-01-01', freq='M')
columns = ['h.' + '{0:>02}'.format(str(h + 1)) for h in range(10)]
forecasts = pd.DataFrame(np.random.randn(120, 10),
index=dates,
columns=columns)
aligned = align_forecast(forecasts.copy(), align='origin')
assert_frame_equal(aligned, forecasts)
aligned = align_forecast(forecasts.copy(), align='target')
direct = forecasts.copy()
for i in range(10):
direct.iloc[(i + 1):, i] = direct.iloc[:(120 - i - 1), i].values
direct.iloc[:(i + 1), i] = np.nan
assert_frame_equal(aligned, direct)
assert_raises(ValueError, align_forecast, forecasts, align='unknown')
def _generate_lag_names(self):
lags = self._lags
names = []
var_name = self._y_series.name
if len(var_name) > 10:
var_name = var_name[:4] + '...' + var_name[-3:]
for i in range(lags.shape[1]):
names.append(var_name + '[' + str(lags[1, i]) + ']')
return names
def test_align(self):
dates = pd.date_range('2000-01-01', '2010-01-01', freq='M')
columns = ['h.' + '{0:>02}'.format(str(h + 1)) for h in range(10)]
forecasts = pd.DataFrame(np.random.randn(120, 10),
index=dates,
columns=columns)
aligned = align_forecast(forecasts.copy(), align='origin')
assert_frame_equal(aligned, forecasts)
aligned = align_forecast(forecasts.copy(), align='target')
direct = forecasts.copy()
for i in range(10):
direct.iloc[(i + 1):, i] = direct.iloc[:(120 - i - 1), i].values
direct.iloc[:(i + 1), i] = np.nan
assert_frame_equal(aligned, direct)
assert_raises(ValueError, align_forecast, forecasts, align='unknown')
def _compute_statistic(self):
overlap, debiased, robust = self._overlap, self._debiased, self._robust
y, nobs, q, trend = self._y, self._nobs, self._lags, self._trend
nq = nobs - 1
if not overlap:
# Check length of y
if nq % q != 0:
extra = nq % q
y = y[:-extra]
warnings.warn(invalid_length_doc.format(var='y',
block=q,
drop=extra),
InvalidLengthWarning)
nobs = y.shape[0]
if trend == 'nc':
mu = 0
else:
mu = (y[-1] - y[0]) / (nobs - 1)
delta_y = diff(y)
nq = delta_y.shape[0]
sigma2_1 = sum((delta_y - mu) ** 2.0) / nq
if not overlap:
delta_y_q = y[q::q] - y[0:-q:q]
sigma2_q = sum((delta_y_q - q * mu) ** 2.0) / nq
self._summary_text = ['Computed with non-overlapping blocks']
else:
delta_y_q = y[q:] - y[:-q]
sigma2_q = sum((delta_y_q - q * mu) ** 2.0) / (nq * q)
self._summary_text = ['Computed with overlapping blocks']
if debiased and overlap:
sigma2_1 *= nq / (nq - 1)
m = q * (nq - q + 1) * (1 - (q / nq))
sigma2_q *= (nq * q) / m
self._summary_text = ['Computed with overlapping blocks '
'(de-biased)']
if not overlap:
self._stat_variance = 2.0 * (q - 1)
elif not robust:
self._stat_variance = (2 * (2 * q - 1) * (q - 1)) / (2 * q)
else:
z2 = (delta_y - mu) ** 2.0
scale = sum(z2) ** 2.0
theta = 0.0
for k in range(1, q):
delta = nq * z2[k:].dot(z2[:-k]) / scale
theta += (1 - k / q) ** 2.0 * delta
self._stat_variance = theta
self._vr = sigma2_q / sigma2_1
self._stat = sqrt(nq) * (self._vr - 1) / sqrt(self._stat_variance)
self._pvalue = 2 - 2 * norm.cdf(abs(self._stat))
def test_garch_power(self):
garch = GARCH(power=1.0)
assert_equal(garch.num_params, 3)
assert_equal(garch.name, 'AVGARCH')
assert_equal(garch.power, 1.0)
sv = garch.starting_values(self.resids)
assert_equal(sv.shape[0], garch.num_params)
bounds = garch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(np.abs(self.resids))))
assert_equal(bounds[1], (0.0, 1.0))
assert_equal(bounds[2], (0.0, 1.0))
var_bounds = garch.variance_bounds(self.resids)
backcast = garch.backcast(self.resids)
w = 0.94 ** np.arange(75)
assert_almost_equal(backcast,
np.sum(np.abs(self.resids[:75]) * (w / w.sum())))
parameters = np.array([.1, .1, .8])
garch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.garch_recursion(parameters,
np.abs(self.resids),
np.sign(self.resids),
cond_var_direct,
1, 0, 1, self.T, backcast, var_bounds)
cond_var_direct **= 2.0 # Square since recursion does not apply power
assert_allclose(self.sigma2, cond_var_direct)
a, b = garch.constraints()
a_target = np.vstack((np.eye(3), np.array([[0, -1.0, -1.0]])))
b_target = np.array([0.0, 0.0, 0.0, -1.0])
assert_array_equal(a, a_target)
assert_array_equal(b, b_target)
state = self.rng.get_state()
rng = Normal()
rng.random_state.set_state(state)
sim_data = garch.simulate(parameters, self.T, rng.simulate([]))
self.rng.set_state(state)
e = self.rng.standard_normal(self.T + 500)
initial_value = 1.0
sigma = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma[t] = parameters[0]
shock = initial_value if t == 0 else np.abs(data[t - 1])
sigma[t] += parameters[1] * shock
lagged_value = initial_value if t == 0 else sigma[t - 1]
sigma[t] += parameters[2] * lagged_value
data[t] = e[t] * sigma[t]
data = data[500:]
sigma2 = sigma[500:] ** 2.0
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
def _check_specification(self):
"""Checks the specification for obvious errors """
if self._x is not None:
if self._x.ndim != 2 or self._x.shape[0] != self._y.shape[0]:
raise ValueError(
'x must be nobs by n, where nobs is the same as '
'the number of elements in y')
def_names = ['x' + str(i) for i in range(self._x.shape[1])]
self._x_names, self._x_index = parse_dataframe(self._x, def_names)
self._x = np.asarray(self._x)
def _check_specification(self):
"""Checks the specification for obvious errors """
if self._x is not None:
if self._x.ndim != 2 or self._x.shape[0] != self._y.shape[0]:
raise ValueError(
'x must be nobs by n, where nobs is the same as '
'the number of elements in y')
def_names = ['x' + str(i) for i in range(self._x.shape[1])]
self._x_names, self._x_index = parse_dataframe(self._x, def_names)
self._x = np.asarray(self._x)
def _autolag_ols(endog, exog, startlag, maxlag, method):
"""
Returns the results for the lag length that maximizes the info criterion.
Parameters
----------
endog : {ndarray, Series}
nobs array containing endogenous variable
exog : {ndarray, DataFrame}
nobs by (startlag + maxlag) array containing lags and possibly other
variables
startlag : int
The first zero-indexed column to hold a lag. See Notes.
maxlag : int
The highest lag order for lag length selection.
method : {'aic', 'bic', 't-stat'}
aic - Akaike Information Criterion
bic - Bayes Information Criterion
t-stat - Based on last lag
Returns
-------
icbest : float
Minimum value of the information criteria
lag : int
The lag length that maximizes the information criterion.
Notes
-----
Does estimation like mod(endog, exog[:,:i]).fit()
where i goes from lagstart to lagstart + maxlag + 1. Therefore, lags are
assumed to be in contiguous columns from low to high lag length with
the highest lag in the last column.
"""
method = method.lower()
q, r = qr(exog)
qpy = q.T.dot(endog)
ypy = endog.T.dot(endog)
xpx = exog.T.dot(exog)
effective_max_lag = min(maxlag, matrix_rank(xpx) - startlag)
sigma2 = empty(effective_max_lag + 1)
tstat = empty(effective_max_lag + 1)
nobs = float(endog.shape[0])
tstat[0] = inf
for i in range(startlag, startlag + effective_max_lag + 1):
b = solve(r[:i, :i], qpy[:i])
sigma2[i - startlag] = (ypy - b.T.dot(xpx[:i, :i]).dot(b)) / nobs
if method == 't-stat' and i > startlag:
xpxi = inv(xpx[:i, :i])
stderr = sqrt(sigma2[i - startlag] * xpxi[-1, -1])
tstat[i - startlag] = b[-1] / stderr
return _select_best_ic(method, nobs, sigma2, tstat)
def test_garch_power(self):
garch = GARCH(power=1.0)
assert_equal(garch.num_params, 3)
assert_equal(garch.name, 'AVGARCH')
assert_equal(garch.power, 1.0)
sv = garch.starting_values(self.resids)
assert_equal(sv.shape[0], garch.num_params)
bounds = garch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(np.abs(self.resids))))
assert_equal(bounds[1], (0.0, 1.0))
assert_equal(bounds[2], (0.0, 1.0))
var_bounds = garch.variance_bounds(self.resids)
backcast = garch.backcast(self.resids)
w = 0.94 ** np.arange(75)
assert_almost_equal(backcast,
np.sum(np.abs(self.resids[:75]) * (w / w.sum())))
parameters = np.array([.1, .1, .8])
garch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.garch_recursion(parameters,
np.abs(self.resids),
np.sign(self.resids),
cond_var_direct,
1, 0, 1, self.T, backcast, var_bounds)
cond_var_direct **= 2.0 # Square since recursion does not apply power
assert_allclose(self.sigma2, cond_var_direct)
A, b = garch.constraints()
A_target = np.vstack((np.eye(3), np.array([[0, -1.0, -1.0]])))
b_target = np.array([0.0, 0.0, 0.0, -1.0])
assert_array_equal(A, A_target)
assert_array_equal(b, b_target)
state = np.random.get_state()
rng = Normal()
sim_data = garch.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 1.0
sigma = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma[t] = parameters[0]
shock = initial_value if t == 0 else np.abs(data[t - 1])
sigma[t] += parameters[1] * shock
lagged_value = initial_value if t == 0 else sigma[t - 1]
sigma[t] += parameters[2] * lagged_value
data[t] = e[t] * sigma[t]
data = data[500:]
sigma2 = sigma[500:] ** 2.0
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
def test_garch_no_lagged_vol(self):
garch = GARCH(p=1, o=1, q=0)
sv = garch.starting_values(self.resids)
assert_equal(sv.shape[0], garch.num_params)
bounds = garch.bounds(self.resids)
assert_equal(bounds[0], (0.0, 10.0 * np.mean(self.resids**2.0)))
assert_equal(bounds[1], (0.0, 1.0))
assert_equal(bounds[2], (-1.0, 2.0))
backcast = garch.backcast(self.resids)
parameters = np.array([.5, .25, .5])
var_bounds = garch.variance_bounds(self.resids)
garch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
rec.garch_recursion(parameters, self.resids**2.0, np.sign(self.resids),
cond_var_direct, 1, 1, 0, self.T, backcast,
var_bounds)
assert_allclose(self.sigma2, cond_var_direct)
A, b = garch.constraints()
A_target = np.vstack((np.eye(3), np.array([[0, -1.0, -0.5]])))
A_target[2, 1] = 1.0
b_target = np.array([0.0, 0.0, 0.0, -1.0])
assert_array_equal(A, A_target)
assert_array_equal(b, b_target)
state = np.random.get_state()
rng = Normal()
sim_data = garch.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 1.0
sigma2 = np.zeros(self.T + 500)
data = np.zeros(self.T + 500)
for t in range(self.T + 500):
sigma2[t] = parameters[0]
shock = initial_value if t == 0 else data[t - 1]**2.0
sigma2[t] += parameters[1] * shock
shock = 0.5 * initial_value if t == 0 else \
(data[t - 1] ** 2.0) * (data[t - 1] < 0)
sigma2[t] += parameters[2] * shock
data[t] = e[t] * np.sqrt(sigma2[t])
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
assert_equal(garch.p, 1)
assert_equal(garch.o, 1)
assert_equal(garch.q, 0)
assert_equal(garch.num_params, 3)
assert_equal(garch.name, 'GJR-GARCH')
def _generate_lag_names(self):
"""Generates lag names. Overridden by other models"""
lags = self._lags
names = []
var_name = self._y_series.name
if len(var_name) > 10:
var_name = var_name[:4] + '...' + var_name[-3:]
for i in range(lags.shape[1]):
names.append(var_name + '[' + str(lags[0, i]) + ':' +
str(lags[1, i]) + ']')
return names
def update_indices(self):
"""
Update indices for the next iteration of the bootstrap. This must
be overridden when creating new bootstraps.
"""
randint = self._random_state.randint
pos_indices = [randint(self._num_arg_items[i], size=self._num_arg_items[i])
for i in range(self._num_args)]
kw_indices = {key: randint(self._num_kw_items[key], size=self._num_kw_items[key])
for key in self._kwargs}
return pos_indices, kw_indices
def _generate_lag_names(self):
"""Generates lag names. Overridden by other models"""
lags = self._lags
names = []
var_name = self._y_series.name
if len(var_name) > 10:
var_name = var_name[:4] + '...' + var_name[-3:]
for i in range(lags.shape[1]):
names.append(
var_name + '[' + str(lags[0, i]) + ':' + str(lags[1, i]) + ']')
return names
def update_indices(self):
"""
Update indices for the next iteration of the bootstrap. This must
be overridden when creating new bootstraps.
"""
randint = self._random_state.randint
pos_indices = [randint(self._num_arg_items[i], size=self._num_arg_items[i])
for i in range(self._num_args)]
kw_indices = {key: randint(self._num_kw_items[key], size=self._num_kw_items[key])
for key in self._kwargs}
return pos_indices, kw_indices
def _ar_to_impulse(steps, params):
p = params.shape[0]
impulse = np.zeros(steps)
impulse[0] = 1
if p == 0:
return impulse
for i in range(1, steps):
k = min(p - 1, i - 1)
st = max(i - p, 0)
impulse[i] = impulse[st:i].dot(params[k::-1])
return impulse
def _reformat_lags(self):
"""
Reformats the input lags to a 2 by m array, which simplifies other
operations. Output is stored in _lags
"""
lags = self.lags
if lags is None:
self._lags = None
return
lags = np.asarray(lags)
if np.any(lags < 0):
raise ValueError("Input to lags must be non-negative")
if lags.ndim == 0:
lags = np.arange(1, lags + 1)
if lags.ndim == 1:
if np.any(lags <= 0):
raise ValueError('When using the 1-d format of lags, values '
'must be positive')
lags = np.unique(lags)
temp = np.array([lags, lags])
if self.use_rotated:
temp[0, 1:] = temp[0, 0:-1]
temp[0, 0] = 0
else:
temp[0, :] = 0
self._lags = temp
elif lags.ndim == 2:
if lags.shape[0] != 2:
raise ValueError('When using a 2-d array, lags must by k by 2')
if np.any(lags[0] < 0) or np.any(lags[1] <= 0):
raise ValueError('Incorrect values in lags')
ind = np.lexsort(np.flipud(lags))
lags = lags[:, ind]
test_mat = zeros((lags.shape[1], np.max(lags)))
for i in range(lags.shape[1]):
test_mat[i, lags[0, i]:lags[1, i]] = 1.0
rank = np.linalg.matrix_rank(test_mat)
if rank != lags.shape[1]:
raise ValueError('lags contains redundant entries')
self._lags = lags
if self.use_rotated:
from warnings import warn
warn('Rotation is not available when using the '
'2-d lags input format')
else:
raise ValueError('Incorrect format for lags')
def test_harx(self):
harx = HARX(self.y, self.x, lags=[1, 5, 22])
params = np.array([1.0, 0.4, 0.3, 0.2, 1.0, 1.0])
data = harx.simulate(params, self.T, x=randn(self.T + 500, 1))
iv = randn(22, 1)
data = harx.simulate(params, self.T, x=randn(self.T + 500, 1),
initial_value=iv)
assert_equal(data.shape, (self.T, 3))
cols = ['data', 'volatility', 'errors']
for c in cols:
assert_true(c in data)
bounds = harx.bounds()
for b in bounds:
assert_equal(b[0], -np.inf)
assert_equal(b[1], np.inf)
assert_equal(len(bounds), 5)
assert_equal(harx.num_params, 1 + 3 + self.x.shape[1])
assert_equal(harx.constant, True)
a, b = harx.constraints()
assert_equal(a, np.empty((0, 5)))
assert_equal(b, np.empty(0))
res = harx.fit()
assert_raises(RuntimeError, res.forecast, horizon=10)
assert_raises(ValueError, res.forecast, params=np.array([1.0, 1.0]))
nobs = self.T - 22
rhs = np.ones((nobs, 5))
y = self.y
lhs = y[22:]
for i in range(self.T - 22):
rhs[i, 1] = y[i + 21]
rhs[i, 2] = np.mean(y[i + 17:i + 22])
rhs[i, 3] = np.mean(y[i:i + 22])
rhs[:, 4] = self.x[22:, 0]
params = np.linalg.pinv(rhs).dot(lhs)
assert_almost_equal(params, res.params[:-1])
assert_equal(harx.first_obs, 22)
assert_equal(harx.last_obs, 1000)
assert_equal(harx.hold_back, None)
assert_equal(harx.lags, [1, 5, 22])
assert_equal(harx.nobs, self.T - 22)
assert_equal(harx.name, 'HAR-X')
assert_equal(harx.use_rotated, False)
harx
harx._repr_html_()
res = harx.fit(cov_type='mle')
res
def test_egarch_100(self):
egarch = EGARCH(p=1, o=0, q=0)
sv = egarch.starting_values(self.resids)
assert_equal(sv.shape[0], egarch.num_params)
backcast = egarch.backcast(self.resids)
w = 0.94 ** np.arange(75)
backcast_test = np.sum((self.resids[:75] ** 2) * (w / w.sum()))
assert_almost_equal(backcast, np.log(backcast_test))
var_bounds = egarch.variance_bounds(self.resids)
parameters = np.array([.1, .4])
egarch.compute_variance(parameters, self.resids, self.sigma2, backcast,
var_bounds)
cond_var_direct = np.zeros_like(self.sigma2)
lnsigma2 = np.empty(self.T)
std_resids = np.empty(self.T)
abs_std_resids = np.empty(self.T)
rec.egarch_recursion(parameters, self.resids, cond_var_direct, 1, 0, 0,
self.T, backcast, var_bounds, lnsigma2,
std_resids, abs_std_resids)
assert_allclose(self.sigma2, cond_var_direct)
state = np.random.get_state()
rng = Normal()
sim_data = egarch.simulate(parameters, self.T, rng.simulate([]))
np.random.set_state(state)
e = np.random.standard_normal(self.T + 500)
initial_value = 0.1 / (1 - 0.95)
lnsigma2 = np.zeros(self.T + 500)
lnsigma2[0] = initial_value
sigma2 = np.zeros(self.T + 500)
sigma2[0] = np.exp(lnsigma2[0])
data = np.zeros(self.T + 500)
data[0] = np.sqrt(sigma2[0]) * e[0]
norm_const = np.sqrt(2 / np.pi)
for t in range(1, self.T + 500):
lnsigma2[t] = parameters[0]
lnsigma2[t] += parameters[1] * (np.abs(e[t - 1]) - norm_const)
sigma2 = np.exp(lnsigma2)
data = e * np.sqrt(sigma2)
data = data[500:]
sigma2 = sigma2[500:]
assert_almost_equal(data - sim_data[0] + 1.0, np.ones_like(data))
assert_almost_equal(sigma2 / sim_data[1], np.ones_like(sigma2))
def reset(self, use_seed=True):
"""
Resets the bootstrap to either its initial state or the last seed.
Parameters
----------
use_seed : bool, optional
Flag indicating whether to use the last seed if provided. If
False or if no seed has been set, the bootstrap will be reset
to the initial state. Default is True
"""
pos_indices = [np.arange(self._num_arg_items[i]) for i in range(self._num_args)]
kw_indices = {key: np.arange(self._num_kw_items[key]) for key in self._kwargs}
self._index = pos_indices, kw_indices
self._resample()
self.random_state.set_state(self._initial_state)
if use_seed and self._seed is not None:
self.seed(self._seed)
return None
def bootstrap(self, reps):
"""
Iterator for use when bootstrapping
Parameters
----------
reps : int
Number of bootstrap replications
Returns
-------
gen : generator
Generator to iterate over in bootstrap calculations
Example
-------
The key steps are problem dependent and so this example shows the use
as an iterator that does not produce any output
>>> from arch.bootstrap import IIDBootstrap
>>> import numpy as np
>>> bs = IIDBootstrap(np.arange(100), x=np.random.randn(100))
>>> for posdata, kwdata in bs.bootstrap(1000):
... # Do something with the positional data and/or keyword data
... pass
.. note::
Note this is a generic example and so the class used should be the
name of the required bootstrap
Notes
-----
The iterator returns a tuple containing the data entered in positional
arguments as a tuple and the data entered using keywords as a
dictionary
"""
for _ in range(reps):
self._index = self.update_indices()
yield self._resample()
