def test_studentpdf():
x = asarray([0.0608528, 0.1296728, -0.2238741, 0.79862108])
mu = asarray([-0.85759774, 0.70178911, -0.29351646, 1.60215909])
var = asarray([0.82608497, 0.75882319, 0.86101641, 0.73113357])
nu = asarray([0.71341641, 0.52532607, 0.20685246, 0.02304925])
p = studentpdf(x, mu, var, nu, nargout=1)
assert allclose(p, asarray([0.1521209, 0.1987373, 0.21214484, 0.01335992]))
(p, dp) = studentpdf(x, mu, var, nu, nargout=2)
assert allclose(p, asarray([0.1521209, 0.1987373, 0.21214484, 0.01335992]))
assert allclose(
dp,
asarray([[1.67068098e-01, 8.00695192e-04, 9.07088043e-02],
[-2.38903047e-01, -4.08902709e-02, 1.76043126e-01],
[9.74584714e-02, -1.19253012e-01, 4.08675818e-01],
[-1.65769327e-02, -2.71641034e-05, 5.45223728e-01]]))
print 'studentpdf Test PASSED'
def test_studentpdf():
x = asarray([0.0608528, 0.1296728, -0.2238741, 0.79862108])
mu = asarray([-0.85759774, 0.70178911, -0.29351646, 1.60215909])
var = asarray([0.82608497, 0.75882319, 0.86101641, 0.73113357])
nu = asarray([0.71341641, 0.52532607, 0.20685246, 0.02304925])
p = studentpdf(x, mu, var, nu, nargout=1)
assert allclose(
p, asarray([0.1521209, 0.1987373, 0.21214484, 0.01335992]))
(p, dp) = studentpdf(x, mu, var, nu, nargout=2)
assert allclose(
p, asarray([0.1521209, 0.1987373, 0.21214484, 0.01335992]))
assert allclose(
dp, asarray([[1.67068098e-01, 8.00695192e-04, 9.07088043e-02],
[-2.38903047e-01, -4.08902709e-02, 1.76043126e-01],
[9.74584714e-02, -1.19253012e-01, 4.08675818e-01],
[-1.65769327e-02, -2.71641034e-05, 5.45223728e-01]]))
print 'studentpdf Test PASSED'
def predict(self,X,needDerivatives=False):
N = self.post_params.shape[0] # 1 x 1
mus = self.post_params[0] # N x 1. [x]
kappas = self.post_params[1] # N x 1. [points]
alphas = self.post_params[2] # N x 1. [points]
betas = self.post_params[3] # N x 1. [x^2]
# TODO verify this is correct by citing reference with posterior predictive
# However, probably correct since we get the same lml under random
# permutations of the data => coherence.
# N x 1. [x^2]
predictive_variance = betas*(kappas+1)/(alphas*kappas)
df = 2.0*alphas # N x 1. [points]
if not needDerivatives:
self.predprobs = studentpdf(xnew, mus, predictive_variance, df) # N x 1. [P/x]
else:
self.predprobs, dtpdf = studentpdf(X, mus, predictive_variance, df, nargout=2) # N x 1. [P/x]
dmu_dtheta = np.transpose(self.dpost_params[0,:,:], axes=[2,1,0]) # N x 4
dkappa_dtheta = np.transpose(self.dpost_params[1,:,:], axes=[2,1,0]) # N x 4
dalpha_dtheta = np.transpose(self.dpost_params[2,:,:], axes=[2,1,0]) # N x 4
dbeta_dtheta = np.transpose(self.dpost_params[3,:,:], axes=[2,1,0]) # N x 4
dnu_dtheta = 2.0 * dalpha_dtheta # N x 4
# TODO use rmult and eliminate the for loop
dpv_dtheta = np.zeros((N, 4))
for ii in range(4):
QRpart = (dbeta_dtheta[:,ii]*alphas - betas*dalpha_dtheta[:,ii])/ alphas**2 # N x 1
dpv_dtheta[:,ii] = -(betas/(alphas*kappas**2))*dkappa_dtheta[:,ii] + (1 + 1/kappas)*QRpart # N x 1
# TODO use rmult and eliminate the for loop
dp_dtheta = np.zeros((N, 4))
for ii in range(4):
# dp/dtheta_i = dp/dmu * dmu/dtheta_i + dp/dsigma2 * dsigma2/dtheta_i +
# dp/dnu + dnu/dtheta_i
# N x 1
dp_dtheta[:,ii] = dtpdf[:,0]*dmu_dtheta[:,ii] + dtpdf[:, 1]*dpv_dtheta[:,ii] + dtpdf[:, 2]*dnu_dtheta[:,ii]
self.dpredprobs = dp_dtheta
def bocpdGPT(
X,
model,
theta_m,
theta_h,
scalePrior,
dt,
):
# Maximum numbers of points considered for predicting the next one regardless of
# the run length and cov function. Set to Inf is we don't care about speed.
maxPossibleLen = 500
num_hazard_params = len(theta_h)
num_model_params = len(theta_m)
assert isKosher(X)
assert dt > 0
(T, D) = X.shape
# Number of time point observed. 1 x 1. [s]
# TODO extend to higher D
assert D == 1
# Never need to consider more than T points in the past. 1 x 1. [points]
maxPossibleLen = min(T, maxPossibleLen)
# Ensure the gamma prior parameters are positive(as required). 2 x 1. []
scalePrior = np.exp(scalePrior)
alpha0 = scalePrior[0]
beta0 = scalePrior[1]
# Evaluate the hazard function:
# H(r) = P(runlength_t=0 | runlength_t - 1=r - 1)
# Pre - computed the hazard in preperation for steps 4 & 5, alg 1, of[RPA]
(H, dH) = logistic_h2(np.asarray(range(1, T + 1)), theta_h)
R = np.zeros((T + 1, T + 1))
S = np.zeros((T, T))
# The standardized square error (SSE) for each runlength.
SSE = np.zeros((T + 1, D))
# The evidence at each time step = > Z(t) = P(X_t | X_1: t - 1).
Z = np.zeros((T, 1))
predMeans = np.zeros((T, 1))
predMed = np.zeros((T, 1))
# At time t = 1, we have complete knowledge about the run length. This assumes
# there was surely a change point right before the first data point not at the
# first data point. Implements step 1, alg 1, of[RPA].
# = > P(runglenth_0=0 | nothing) = 1
R[0, 0] = 1
# Initialize first SSE to contribution from gamma prior.
SSE[0] = 2 * beta0
# Precompute all the gpr aspects of algorithm.
(alpha, sigma2, dalpha, dsigma2) = gpr1step5(theta_m, model,
maxPossibleLen, dt)
maxLen = alpha.shape[0]
sigma2 = np.concatenate((sigma2, sigma2[-1, 0] * np.ones(
(T - sigma2.shape[0], 1))))
for t in range(1, T + 1):
# Implictly Implements step 2, alg 1, of[RPA]: oberserve new datum, simply
# by incrementing the loop index.
# Evaluate the predictive distribution for the new datum under each of the
# parameters. Implements step 3, alg 1, of[RPA]. predprobs(r)
# = p(X(t) | X(1: t - 1), runlength_t - 1=r - 1). t x 1. [P]
MRC = min(maxLen, t) # How many points back to look when predicting
mu = np.dot(alpha[:MRC, :MRC - 1], X[t - MRC:t - 1,
0][::-1]) # MRC x 1. [x]
# Extend the mu (mean) prediction for the older (> MRC) run length
# hypothesis
if MRC < t:
mu = np.append(mu, mu[-1] *
np.ones(t - mu.shape[0])) # t - MRC x 1. [x]
df = np.asarray([2 * alpha0]) + np.asarray(range(t))
pred_var = sigma2[:t, 0] * SSE[:t, 0] / df
predprobs = studentpdf(X[t - 1, 0], mu, pred_var, df, 1)
# Update the SSE for each run length
SSE[1:t + 1, 0] = SSE[:t, 0] + (mu - X[t - 1, 0])**2 / sigma2[:t, 0]
SSE[0, 0] = 2 * beta0 # 1 x 1. []
predMeans[t - 1] = np.dot(R[:mu.shape[0], t - 1].T, mu)
# The following is pretty slow
#np.median(MoTrnd(R[:mu.shape[0], t - 1], mu, pred_var[:mu.shape[0]], df[:mu.shape[0]], 1000))
predMed[t - 1] = 0
# Evaluate the growth probabilities - shift the probabilities up and to the
# right, scaled by the hazard function and the predictive
# probabilities.
R[1:t + 1, t] = R[:t, t - 1] * predprobs * (1 - H[:t])
# Evaluate the probability that there * was * a changepoint and we're
# accumulating the mass back down at r = 0.
R[0, t] = (R[:t, t - 1] * predprobs * H[:t]).sum()
# Renormalize the run length probabilities for improved numerical stability.
# Note that unlike in [RPA] which keeps track of P(r_t, X_1: t), we keep track
# of P(r_t | X_1: t) = > unnormalized R(i, t + 1) = P(runlength_t=i - 1 | X_1: t)
# * P(X_t | X_1: t - 1) = > normalization const Z(t) = P(X_t | X_1: t - 1). Sort of
# Implements step 6, alg 1, of[RPA].
Z[t - 1] = R[:t + 1, t].sum()
R[:t + 1, t] /= Z[t - 1]
# Get the S matrix
S[:t, t - 1] = R[:t, t - 1] * predprobs
S[:, t - 1] = S[:, t - 1] / S[:, t - 1].sum()
# endTloop
# Get the negative log marginal likelihood of the data, X(1: end), under
# the model = P(X_1: T), integrating out all the runlengths. 1 x 1. [log
# P]
nlml = -sum(np.log(Z))
return (R, S, nlml, Z, predMeans, predMed)
def bocpdGPT_trunc(
X,
model,
theta_m,
theta_h,
scalePrior,
dt,
):
# Maximum numbers of points considered for predicting the next one regardless of
# the run length and cov function. Set to Inf is we don't care about speed.
maxPossibleLen = 500
num_hazard_params = len(theta_h)
num_model_params = len(theta_m)
assert isKosher(X)
assert dt > 0
(T, D) = X.shape
# Number of time point observed. 1 x 1. [s]
# TODO extend to higher D
assert D == 1
# Never need to consider more than T points in the past. 1 x 1. [points]
maxPossibleLen = min(T, maxPossibleLen)
# Ensure the gamma prior parameters are positive(as required). 2 x 1. []
scalePrior = np.exp(scalePrior)
alpha0 = scalePrior[0]
beta0 = scalePrior[1]
# Precompute all the gpr aspects of algorithm. [maxLen x maxLen, maxLen x
# 1]
(alpha, sigma2, dalpha, dsigma2) = gpr1step5(theta_m, model,
maxPossibleLen, dt)
maxLen = alpha.shape[0]
assert maxLen >= 1
# Evaluate the hazard function:
# H(r) = P(runlength_t=0 | runlength_t - 1=r - 1)
# Pre - computed the hazard in preperation for steps 4 & 5, alg 1, of[RPA]
(H, dH) = logistic_h2(np.asarray(range(1, maxLen + 1)), theta_h)
R = np.zeros((maxLen + 1, T + 1))
# The standardized square error for each runlength.
SSE = np.zeros((maxLen, D))
# The evidence at each time step = > Z(t) = P(X_t | X_1: t - 1).
Z = np.zeros((T, 1))
predMeans = np.zeros((T, 1))
predMed = np.zeros((T, 1))
# At time t = 1, we have complete knowledge about the run length. This assumes
# there was surely a change point right before the first data point not at the
# first data point. Implements step 1, alg 1, of[RPA].
# = > P(runglenth_0=0 | nothing) = 1
R[0, 0] = 1
# Initialize first SSE to contribution from gamma prior.
SSE[0] = 2 * beta0
# How many degrees of freedom in the prediction for each run length.
df = np.asarray([2 * alpha0]) + np.asarray(range(maxLen))
for t in range(1, T + 1):
# Implictly Implements step 2, alg 1, of[RPA]: oberserve new datum, simply
# by incrementing the loop index.
# Evaluate the predictive distribution for the new datum under each of the
# parameters. Implements step 3, alg 1, of[RPA]. predprobs(r)
# = p(X(t) | X(1: t - 1), runlength_t - 1=r - 1). t x 1. [P]
predprobs = np.zeros(maxLen)
if t < maxLen:
mu = np.dot(alpha[:t, :t], X[:t, 0][::-1])
# The predictive variance for each prediction
pred_var = sigma2[:t, 0] * SSE[:t, 0] / df[:t]
# get the posterior predictive probability for each run length
predprobs[:t] = studentpdf(X[t - 1, 0], mu, pred_var, df[:t], 1)
# Update the SSE for each run length
SSE[1:t + 1, 0] = SSE[:t, 0] + \
(mu - X[t - 1, 0]) ** 2 / sigma2[:t, 0]
SSE[0, 0] = 2 * beta0 # 1 x 1. []
else:
mu = np.dot(alpha, X[t - maxLen + 1:t, 0][::-1])
# The predictive variance for each prediction
pred_var = sigma2[:, 0] * SSE[:, 0] / df
# get the posterior predictive probability for each run length
predprobs = studentpdf(X[t - 1, 0], mu, pred_var, df, 1)
# Update the SSE for each run length
SSE[1:maxLen, 0] = SSE[:maxLen - 1, 0] + \
(mu[:maxLen - 1] - X[maxLen - 1, 0]) ** 2 / \
sigma2[:maxLen - 1, 0]
SSE[0, 0] = 2 * beta0
# endif
predMeans[t - 1] = np.dot(R[:mu.shape[0], t - 1].T, mu)
predMed[t - 1] = np.median(
MoTrnd(R[:mu.shape[0], t - 1], mu, pred_var[:mu.shape[0]], df[:mu.shape[0]], 1000))
# Evaluate the growth probabilities - shift the probabilities up and to the
# right, scaled by the hazard function and the predictive
# probabilities.
R[1:, t] = R[: maxLen, t - 1] * predprobs * (1 - H[: maxLen])
# Evaluate the probability that there * was * a changepoint and we're
# accumulating the mass back down at r = 0.
R[0, t] = (R[: maxLen, t - 1] * predprobs * H[: maxLen]).sum()
# Renormalize the run length probabilities for improved numerical stability.
# Note that unlike in [RPA] which keeps track of P(r_t, X_1: t), we keep track
# of P(r_t | X_1: t) = > unnormalized R(i, t + 1) = P(runlength_t=i - 1 | X_1: t)
# * P(X_t | X_1: t - 1) = > normalization const Z(t) = P(X_t | X_1: t - 1). Sort of
# Implements step 6, alg 1, of[RPA].
Z[t - 1] = R[:, t].sum()
R[: maxLen, t] /= Z[t - 1]
R[maxLen - 1, t] = R[maxLen - 1, t] + R[maxLen, t]
R[maxLen, t] = 0
# endTloop
# Get the negative log marginal likelihood of the data, X(1: end), under
# the model = P(X_1: T), integrating out all the runlengths. 1 x 1. [log
# P]
nlml = -sum(np.log(Z))
return (R, nlml, Z, predMeans, predMed)
