quantecon.arma: Move scipy.signal to ARMA class definition

rht · rht · commit 391b9d8d8539 · 2018-12-12T10:45:04.000Z
diff --git a/quantecon/arma.py b/quantecon/arma.py
@@ -6,7 +6,6 @@
 """
 import numpy as np
 from numpy import conj, pi
-from scipy.signal import dimpulse, freqz, dlsim
 from .util import check_random_state
 
 
@@ -61,6 +60,7 @@ class ARMA:
         processing we desire.  Corresponds with the theta values
 
     """
+    from scipy.signal import dimpulse, freqz, dlsim
 
     def __init__(self, phi, theta=0, sigma=1):
         self._phi, self._theta = phi, theta
@@ -166,7 +166,7 @@ def impulse_response(self, impulse_length=30):
 
         """
         sys = self.ma_poly, self.ar_poly, 1
-        times, psi = dimpulse(sys, n=impulse_length)
+        times, psi = ARMA.dimpulse(sys, n=impulse_length)
         psi = psi[0].flatten()  # Simplify return value into flat array
 
         return psi
@@ -205,7 +205,7 @@ def spectral_density(self, two_pi=True, res=1200):
             The frequency response
 
         """
-        w, h = freqz(self.ma_poly, self.ar_poly, worN=res, whole=two_pi)
+        w, h = ARMA.freqz(self.ma_poly, self.ar_poly, worN=res, whole=two_pi)
         spect = h * conj(h) * self.sigma**2
 
         return w, spect
@@ -253,6 +253,6 @@ def simulation(self, ts_length=90, random_state=None):
 
         sys = self.ma_poly, self.ar_poly, 1
         u = random_state.randn(ts_length, 1) * self.sigma
-        vals = dlsim(sys, u)[1]
+        vals = ARMA.dlsim(sys, u)[1]
 
         return vals.flatten()
