BF: Product and variance would change TimeArray units.

We raise an error instead of doing that.

nitime/tests/test_timeseries.py

@@ -89,6 +89,8 @@ def test_TimeArray_math():
     tnew = timeunits + range(10)
     npt.assert_equal(tnew, timeunits+time1) # recall that time1 was 0-10ms
 
+
+
 def test_TimeArray_comparison():
     "Comparison with unitless quantities should convert to TimeArray units"
     time = ts.TimeArray(range(10), time_unit='ms')
@@ -901,3 +903,11 @@ def test_timearray_math_functions():
             # comparison with unitless should convert to the TimeArray's units
             assert getattr(b, f)() == getattr(a,f)()
 
+def test_timearray_var_prod():
+    """
+    Variance and product change the TimeArray units, so they are not
+    implemented and raise an error
+    """
+    a = ts.TimeArray(range(10))
+    npt.assert_raises(NotImplementedError, a.var)
+    npt.assert_raises(NotImplementedError, a.prod)

nitime/timeseries.py

@@ -269,7 +269,7 @@ def __ge__(self,val):
     def __eq__(self,val):
         val = self._convert_if_needed(val)
         return np.ndarray.__eq__(self,val)
-
+    
     def min(self, *args,**kwargs):
         ret = TimeArray(np.ndarray.min(self, *args,**kwargs),
             time_unit=base_unit)
@@ -299,12 +299,17 @@ def sum(self, *args,**kwargs):
             time_unit=base_unit)
         ret.convert_unit(self.time_unit)
         return ret
-
+
+    def prod(self, *args, **kwargs):
+        e_s = "Product computation changes TimeArray units"
+        raise NotImplementedError(e_s)
+
+
     def var(self, *args, **kwargs):
-        tmp = np.array(self, np.float) / self._conversion_factor
-        ret = TimeArray(tmp.var(*args,**kwargs), time_unit=self.time_unit)
-        return ret
+        e_s = "Variance computation changes TimeArray units"
+        raise NotImplementedError(e_s)
 
+
     def std(self, *args, **kwargs):
         """Returns the standard deviation of this TimeArray (with time units)
 
@@ -314,6 +319,8 @@ def std(self, *args, **kwargs):
             time_unit=base_unit)
         ret.convert_unit(self.time_unit)
         return ret
+
+
     def index_at(self, t, tol=None, mode='closest'):
         """ Returns the integer indices that corresponds to the time t