def estimate_bivariate_mle_jr():
ndim = 2
size = (10000, ndim)
data = np.random.normal(size=size)
eta, lam = 4, -.9
skst = SkewStudent(eta=eta, lam=lam)
data = skst.rvs(size=size)
model = SkStJR(ndim=ndim, data=data)
out = model.fit_mle()
print(out)
model.from_theta(out.x)
fig, axes = plt.subplots(nrows=size[1], ncols=1)
for innov, ax in zip(data.T, axes):
sns.kdeplot(innov, ax=ax, label='data')
lines = [ax.get_lines()[0].get_xdata() for ax in axes]
lines = np.vstack(lines).T
marginals = model.marginals(lines)
for line, margin, ax in zip(lines.T, marginals.T, axes):
ax.plot(line, margin, label='fitted')
ax.legend()
plt.show()
def estimate_bivariate_mle_jr():
ndim = 2
size = (10000, ndim)
data = np.random.normal(size=size)
eta, lam = 4, -.9
skst = SkewStudent(eta=eta, lam=lam)
data = skst.rvs(size=size)
model = SkStJR(ndim=ndim, data=data)
out = model.fit_mle()
print(out)
model.from_theta(out.x)
fig, axes = plt.subplots(nrows=size[1], ncols=1)
for innov, ax in zip(data.T, axes):
sns.kdeplot(innov, ax=ax, label='data')
lines = [ax.get_lines()[0].get_xdata() for ax in axes]
lines = np.vstack(lines).T
marginals = model.marginals(lines)
for line, margin, ax in zip(lines.T, marginals.T, axes):
ax.plot(line, margin, label='fitted')
ax.legend()
plt.show()
def simulate_bekk(param, nobs=1000, distr='normal', degf=10, lam=0):
"""Simulate data.
Parameters
----------
param : BEKKParams instance
Attributes of this class hold parameter matrices
nobs : int
Number of observations to generate. Time series length
distr : str
Name of the distribution from which to generate innovations.
Must be
- 'normal'
- 'student'
- 'skewt'
degf : int
Degrees of freedom for Student or SkewStudent distributions
lam : float
Skewness parameter for Student or SkewStudent distributions.
Must be between (-1, 1)
Returns
-------
innov : (nobs, nstocks) array
Multivariate innovation matrix
"""
nstocks = param.amat.shape[0]
if distr == 'normal':
# Normal innovations
mean, cov = np.zeros(nstocks), np.eye(nstocks)
error = np.random.multivariate_normal(mean, cov, nobs)
elif distr == 'student':
# Student innovations
error = np.random.standard_t(degf, size=(nobs, nstocks))
elif distr == 'skewt':
# Skewed Student innovations
error = SkewStudent(eta=degf, lam=lam).rvs(size=(nobs, nstocks))
else:
raise ValueError('Unknown distribution!')
# Standardize innovations
error = (error - error.mean(0)) / error.std(0)
hvar = np.empty((nobs, nstocks, nstocks))
innov = np.zeros((nobs, nstocks))
hvar[0] = param.get_uvar()
intercept = param.cmat.dot(param.cmat.T)
for i in range(1, nobs):
innov2 = innov[i-1, np.newaxis].T * innov[i-1]
hvar[i] = intercept + param.amat.dot(innov2).dot(param.amat.T) \
+ param.bmat.dot(hvar[i-1]).dot(param.bmat.T)
hvar12 = sl.cholesky(hvar[i], 1)
innov[i] = hvar12.dot(np.atleast_2d(error[i]).T).flatten()
return innov, hvar
def estimate_bivariate_mle_bl():
ndim = 2
size = (10000, ndim)
data = np.random.normal(size=size)
eta, lam = 4, -.9
skst = SkewStudent(eta=eta, lam=lam)
data = skst.rvs(size=size)
model = SkStBL(ndim=ndim, data=data)
out = model.fit_mle(method='L-BFGS-B')
print(out)
def test_ppf(self):
"""Test ppf method."""
skewt = SkewStudent()
num = 50
arg = np.linspace(.01, .99, num)
ppf = skewt.ppf(arg)
self.assertEqual(ppf.shape[0], num)
self.assertIsInstance(skewt.ppf(.5), float)
def estimate_bivariate_mle_bl():
ndim = 2
size = (10000, ndim)
data = np.random.normal(size=size)
eta, lam = 4, -.9
skst = SkewStudent(eta=eta, lam=lam)
data = skst.rvs(size=size)
model = SkStBL(ndim=ndim, data=data)
out = model.fit_mle(method='L-BFGS-B')
print(out)
def test_ppf(self):
"""Test ppf method."""
skewt = SkewStudent()
num = 50
arg = np.linspace(.01, .99, num)
ppf = skewt.ppf(arg)
self.assertEqual(ppf.shape[0], num)
self.assertIsInstance(skewt.ppf(.5), float)
def test_cdf(self):
"""Test cdf method."""
skewt = SkewStudent()
num = 50
arg = np.linspace(-1, 1, num)
cdf = skewt.cdf(arg)
self.assertEqual(cdf.shape[0], num)
self.assertIsInstance(skewt.cdf(0), float)
def test_cdf(self):
"""Test cdf method."""
skewt = SkewStudent()
num = 50
arg = np.linspace(-1, 1, num)
cdf = skewt.cdf(arg)
self.assertEqual(cdf.shape[0], num)
self.assertIsInstance(skewt.cdf(0), float)
def test_init(self):
"""Test __init__."""
skewt = SkewStudent()
self.assertIsInstance(skewt.eta, float)
self.assertIsInstance(skewt.lam, float)
eta, lam = 5., -.2
skewt = SkewStudent(eta=eta, lam=lam)
self.assertEqual(skewt.eta, eta)
self.assertEqual(skewt.lam, lam)
def test_compare_with_t(self):
"""Compare with standard t distribution."""
eta = 5
skewt = SkewStudent(eta=eta, lam=0)
scale = 1/(eta/(eta-2))**.5
standt = t(eta, scale=scale)
arg = np.linspace(-2, 2, 100)
np.testing.assert_array_almost_equal(skewt.pdf(arg), standt.pdf(arg))
np.testing.assert_array_almost_equal(skewt.cdf(arg), standt.cdf(arg))
arg = np.linspace(.01, .99, 100)
np.testing.assert_array_almost_equal(skewt.ppf(arg), standt.ppf(arg))
def test_compare_with_t(self):
"""Compare with standard t distribution."""
eta = 5
skewt = SkewStudent(eta=eta, lam=0)
scale = 1 / (eta / (eta - 2))**.5
standt = t(eta, scale=scale)
arg = np.linspace(-2, 2, 100)
np.testing.assert_array_almost_equal(skewt.pdf(arg), standt.pdf(arg))
np.testing.assert_array_almost_equal(skewt.cdf(arg), standt.cdf(arg))
arg = np.linspace(.01, .99, 100)
np.testing.assert_array_almost_equal(skewt.ppf(arg), standt.ppf(arg))
def test_rvs(self):
"""Test ppf method."""
skewt = SkewStudent()
rvs = skewt.rvs()
self.assertIsInstance(rvs, float)
size = 2
rvs = skewt.rvs(size=size)
self.assertIsInstance(rvs, np.ndarray)
self.assertEqual(rvs.shape, (size, ))
size = (2, 3)
rvs = skewt.rvs(size=size)
self.assertIsInstance(rvs, np.ndarray)
self.assertEqual(rvs.shape, size)
def test_rvs(self):
"""Test ppf method."""
skewt = SkewStudent()
rvs = skewt.rvs()
self.assertIsInstance(rvs, float)
size = 2
rvs = skewt.rvs(size=size)
self.assertIsInstance(rvs, np.ndarray)
self.assertEqual(rvs.shape, (size, ))
size = (2, 3)
rvs = skewt.rvs(size=size)
self.assertIsInstance(rvs, np.ndarray)
self.assertEqual(rvs.shape, size)
# -*- coding: utf-8 -*-
"""Examples.
"""
from __future__ import print_function, division
import numpy as np
import matplotlib.pylab as plt
import seaborn as sns
from scipy.optimize import minimize
from skewstudent import SkewStudent
if __name__ == '__main__':
eta, lam = 5, -.5
param = [eta, lam]
sns.set_context('paper')
skewt = SkewStudent(eta=eta, lam=lam)
data = skewt.rvs(2000)
sns.kdeplot(data)
plt.show()
bounds = [(2.01, 300), (-1, 1)]
res = minimize(skewt.loglikelihood, [10, 0], args=(data,), method='SLSQP',
bounds=bounds)
print(res)
