[Scipy-svn] r7125 - in trunk/scipy/signal: . tests

[scipy-svn at scipy.org]

Author: warren.weckesser
Date: 2011-02-06 13:11:27 -0600 (Sun, 06 Feb 2011)
New Revision: 7125

Modified:
   trunk/scipy/signal/filter_design.py
   trunk/scipy/signal/tests/test_filter_design.py
Log:
BUG: signal: zpk2tf returns a scalar 1.0 for the denominator when the list of poles was empty (ticket #990).  Thanks to asomers for the patch.

Modified: trunk/scipy/signal/filter_design.py
===================================================================
--- trunk/scipy/signal/filter_design.py	2011-02-04 18:32:04 UTC (rev 7124)
+++ trunk/scipy/signal/filter_design.py	2011-02-06 19:11:27 UTC (rev 7125)
@@ -243,7 +243,7 @@
             b[i] = k[i] * poly(z[i])
     else:
         b = k * poly(z)
-    a = poly(p)
+    a = atleast_1d(poly(p))
     return b, a
 
 def normalize(b, a):

Modified: trunk/scipy/signal/tests/test_filter_design.py
===================================================================
--- trunk/scipy/signal/tests/test_filter_design.py	2011-02-04 18:32:04 UTC (rev 7124)
+++ trunk/scipy/signal/tests/test_filter_design.py	2011-02-06 19:11:27 UTC (rev 7125)
@@ -1,9 +1,10 @@
 import warnings
 
 import numpy as np
-from numpy.testing import TestCase, assert_array_almost_equal, assert_raises
+from numpy.testing import TestCase, assert_array_almost_equal, \
+        assert_array_equal, assert_raises, assert_
 
-from scipy.signal import tf2zpk, bessel, BadCoefficients
+from scipy.signal import tf2zpk, zpk2tf, bessel, BadCoefficients
 
 
 class TestTf2zpk(TestCase):
@@ -32,3 +33,22 @@
             assert_raises(BadCoefficients, tf2zpk, [1e-15], [1.0, 1.0])
         finally:
             warnings.simplefilter("always", BadCoefficients)
+
+
+class TestZpk2Tf(TestCase):
+
+    def test_identity(self):
+        """Test the identity transfer function."""
+        z = []
+        p = []
+        k = 1.
+        b, a = zpk2tf(z, p, k)
+        b_r = np.array([1.])  # desired result
+        a_r = np.array([1.])  # desired result
+        # The test for the *type* of the return values is a regression
+        # test for ticket #1095.  In the case p=[], zpk2tf used to
+        # return the scalar 1.0 instead of array([1.0]).
+        assert_array_equal(b, b_r)
+        assert_(isinstance(b, np.ndarray))
+        assert_array_equal(a, a_r)
+        assert_(isinstance(a, np.ndarray))