def test_simulate(): # Test for simulation of new time-series from scipy.signal import lfilter # Common parameters nsimulations = 10 sigma2 = 2 measurement_shocks = np.zeros(nsimulations) state_shocks = np.random.normal(scale=sigma2**0.5, size=nsimulations) # Random walk model, so simulated series is just the cumulative sum of # the shocks mod = KalmanFilter(k_endog=1, k_states=1) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate(nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks)[0].squeeze() desired = np.r_[0, np.cumsum(state_shocks)[:-1]] assert_allclose(actual, desired) # Local level model, so simulated series is just the cumulative sum of # the shocks plus the measurement shock mod = KalmanFilter(k_endog=1, k_states=1) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate(nsimulations, measurement_shocks=np.ones(nsimulations), state_shocks=state_shocks)[0].squeeze() desired = np.r_[1, np.cumsum(state_shocks)[:-1] + 1] assert_allclose(actual, desired) # Local level-like model with observation and state intercepts, so # simulated series is just the cumulative sum of the shocks minus the state # intercept, plus the observation intercept and the measurement shock mod = KalmanFilter(k_endog=1, k_states=1) mod['obs_intercept', 0, 0] = 5. mod['design', 0, 0] = 1. mod['state_intercept', 0, 0] = -2. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate(nsimulations, measurement_shocks=np.ones(nsimulations), state_shocks=state_shocks)[0].squeeze() desired = np.r_[1 + 5, np.cumsum(state_shocks - 2)[:-1] + 1 + 5] assert_allclose(actual, desired) # Model with time-varying observation intercept mod = KalmanFilter(k_endog=1, k_states=1, nobs=10) mod['obs_intercept'] = (np.arange(10) * 1.).reshape(1, 10) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate(nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks)[0].squeeze() desired = np.r_[0, np.cumsum(state_shocks)[:-1] + np.arange(1, 10)] assert_allclose(actual, desired) # Model with time-varying observation intercept, check that error is raised # if more simulations are requested than are nobs. mod = KalmanFilter(k_endog=1, k_states=1, nobs=10) mod['obs_intercept'] = (np.arange(10) * 1.).reshape(1, 10) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. assert_raises(ValueError, mod.simulate, nsimulations + 1, measurement_shocks, state_shocks) # ARMA(1,1): phi = [0.1], theta = [0.5], sigma^2 = 2 phi = np.r_[0.1] theta = np.r_[0.5] mod = sarimax.SARIMAX([0], order=(1, 0, 1)) mod.update(np.r_[phi, theta, sigma2]) actual = mod.ssm.simulate(nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks)[0].squeeze() desired = lfilter([1, theta], [1, -phi], np.r_[0, state_shocks[:-1]]) assert_allclose(actual, desired) # SARIMAX(1,0,1)x(1,0,1,4), this time using the results object call mod = sarimax.SARIMAX([0.1, 0.5, -0.2], order=(1, 0, 1), seasonal_order=(1, 0, 1, 4)) res = mod.filter([0.1, 0.5, 0.2, -0.3, 1]) actual = res.simulate(nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks).squeeze() desired = lfilter(res.polynomial_reduced_ma, res.polynomial_reduced_ar, np.r_[0, state_shocks[:-1]]) assert_allclose(actual, desired)
def test_simulate(): # Test for simulation of new time-series from scipy.signal import lfilter # Common parameters nsimulations = 10 sigma2 = 2 measurement_shocks = np.zeros(nsimulations) state_shocks = np.random.normal(scale=sigma2**0.5, size=nsimulations) # Random walk model, so simulated series is just the cumulative sum of # the shocks mod = KalmanFilter(k_endog=1, k_states=1) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate( nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks)[0].squeeze() desired = np.r_[0, np.cumsum(state_shocks)[:-1]] assert_allclose(actual, desired) # Local level model, so simulated series is just the cumulative sum of # the shocks plus the measurement shock mod = KalmanFilter(k_endog=1, k_states=1) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate( nsimulations, measurement_shocks=np.ones(nsimulations), state_shocks=state_shocks)[0].squeeze() desired = np.r_[1, np.cumsum(state_shocks)[:-1] + 1] assert_allclose(actual, desired) # Local level-like model with observation and state intercepts, so # simulated series is just the cumulative sum of the shocks minus the state # intercept, plus the observation intercept and the measurement shock mod = KalmanFilter(k_endog=1, k_states=1) mod['obs_intercept', 0, 0] = 5. mod['design', 0, 0] = 1. mod['state_intercept', 0, 0] = -2. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate( nsimulations, measurement_shocks=np.ones(nsimulations), state_shocks=state_shocks)[0].squeeze() desired = np.r_[1 + 5, np.cumsum(state_shocks - 2)[:-1] + 1 + 5] assert_allclose(actual, desired) # Model with time-varying observation intercept mod = KalmanFilter(k_endog=1, k_states=1, nobs=10) mod['obs_intercept'] = (np.arange(10)*1.).reshape(1, 10) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. actual = mod.simulate( nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks)[0].squeeze() desired = np.r_[0, np.cumsum(state_shocks)[:-1] + np.arange(1,10)] assert_allclose(actual, desired) # Model with time-varying observation intercept, check that error is raised # if more simulations are requested than are nobs. mod = KalmanFilter(k_endog=1, k_states=1, nobs=10) mod['obs_intercept'] = (np.arange(10)*1.).reshape(1, 10) mod['design', 0, 0] = 1. mod['transition', 0, 0] = 1. mod['selection', 0, 0] = 1. assert_raises(ValueError, mod.simulate, nsimulations+1, measurement_shocks, state_shocks) # ARMA(1,1): phi = [0.1], theta = [0.5], sigma^2 = 2 phi = np.r_[0.1] theta = np.r_[0.5] mod = sarimax.SARIMAX([0], order=(1,0,1)) mod.update(np.r_[phi, theta, sigma2]) actual = mod.ssm.simulate( nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks)[0].squeeze() desired = lfilter([1, theta], [1, -phi], np.r_[0, state_shocks[:-1]]) assert_allclose(actual, desired) # SARIMAX(1,0,1)x(1,0,1,4), this time using the results object call mod = sarimax.SARIMAX([0.1, 0.5, -0.2], order=(1,0,1), seasonal_order=(1,0,1,4)) res = mod.filter([0.1, 0.5, 0.2, -0.3, 1]) actual = res.simulate( nsimulations, measurement_shocks=measurement_shocks, state_shocks=state_shocks).squeeze() desired = lfilter( res.polynomial_reduced_ma, res.polynomial_reduced_ar, np.r_[0, state_shocks[:-1]]) assert_allclose(actual, desired)