[Scipy-svn] r4970 - in trunk/scipy/signal: . tests

[scipy-svn at scipy.org]

Author: stefan
Date: 2008-11-03 13:50:36 -0600 (Mon, 03 Nov 2008)
New Revision: 4970

Added:
   trunk/scipy/signal/tests/test_waveforms.py
Modified:
   trunk/scipy/signal/waveforms.py
Log:
Fix initial value of logarithmic chirp [patch by Christian Christelis].
Closes #547.

Added: trunk/scipy/signal/tests/test_waveforms.py
===================================================================
--- trunk/scipy/signal/tests/test_waveforms.py	2008-11-03 19:39:36 UTC (rev 4969)
+++ trunk/scipy/signal/tests/test_waveforms.py	2008-11-03 19:50:36 UTC (rev 4970)
@@ -0,0 +1,14 @@
+#this program corresponds to special.py
+
+import numpy as np
+from numpy.testing import *
+
+import scipy.signal as signal
+
+class TestChirp(TestCase):
+    def test_log_chirp_at_zero(self):
+        assert_almost_equal(signal.waveforms.chirp(t=0, method='log'),
+                            1.0)
+
+if __name__ == "__main__":
+    run_module_suite()

Modified: trunk/scipy/signal/waveforms.py
===================================================================
--- trunk/scipy/signal/waveforms.py	2008-11-03 19:39:36 UTC (rev 4969)
+++ trunk/scipy/signal/waveforms.py	2008-11-03 19:50:36 UTC (rev 4970)
@@ -177,7 +177,7 @@
                 "For a logarithmic sweep, f1=%f must be larger than f0=%f."
                 % (f1, f0))
         beta = log10(f1-f0)/t1
-        phase_angle = 2*pi * (f0*t + pow(10,beta*t)/(beta*log(10)))
+        phase_angle = 2*pi * (f0*t + (pow(10,beta*t)-1)/(beta*log(10)))
     else:
         raise ValueError("method must be 'linear', 'quadratic', or "
             "'logarithmic' but a value of %r was given." % method)