Changeset 491

Timestamp:

08/23/11 15:40:20 (9 months ago)

Author:

emuller

Message:

Added AnalogSignal?.cov

Location:

trunk

Files:

• src/signals/analogs.py (modified) (2 diffs)
• test/test_analogs.py (modified) (1 diff)

trunk/src/signals/analogs.py

@@ -403 +403 @@
             >> print len(res)
                 4
+
+        Author: Eilif Muller
         """
         if isinstance(events, SpikeTrain):
@@ -421 +423 @@
         if t_last<self.t_stop:
             yield self.time_slice(t_last, self.t_stop)
+
+    def cov(self,signal):
+        """
+
+        Returns the covariance of two signals (self, signal),
+
+        i.e. mean(self.signal*signal)-mean(self.signal)*(mean(signal)
+
+
+        Inputs:
+            signal  - Another AnalogSignal object.  It should have the same temporal dimension
+                      and dt.
+        
+        Examples:
+            >> a1 = AnalogSignal(numpy.random.normal(size=1000),dt=0.1)
+            >> a2 = AnalogSignal(numpy.random.normal(size=1000),dt=0.1)
+            >> print a1.cov(a2)
+            -0.043763817072107143
+            >> print a1.cov(a1)
+            1.0063757246782141
+
+        See also:
+            NeuroTools.analysis.ccf
+            http://en.wikipedia.org/wiki/Covariance
+
+        Author: Eilif Muller
+
+        """
+
+        from numpy import mean
+
+        assert signal.dt == self.dt
+        assert signal.duration()==self.duration()
+
+        return mean(self.signal*signal.signal)-mean(self.signal)*(mean(signal.signal))
+    
 
 

trunk/test/test_analogs.py

@@ -85 +85 @@
         assert res3[0].duration() == 950.0
 
+    def testCovariance(self):
+        a1 = analogs.AnalogSignal(numpy.random.normal(size=10000),dt=0.1)
+        a2 = analogs.AnalogSignal(numpy.random.normal(size=10000),dt=0.1)
+        assert a1.cov(a2) < 0.5
+        assert a1.cov(a1) > 0.5