fixing bug in how negative values would be compared with epsilon percent

git-svn-id: https://svn.ssec.wisc.edu/repos/glance/trunk@140 8a9318a1-56ba-4d59-b755-99d26321be01

pyglance/glance/data.py

@@ -261,11 +261,9 @@ class DiffInfoObject (object) :
         # the valid data which is too different between the two sets according to the given epsilon
         outside_epsilon_mask = np.zeros(shape, dtype=np.bool)
         if (epsilonValue   is not None) :
-            outside_epsilon_mask = outside_epsilon_mask |  \
-                                   (abs(raw_diff) > epsilonValue) & valid_in_both
+            outside_epsilon_mask |= (abs(raw_diff) > epsilonValue) & valid_in_both
         if (epsilonPercent is not None) :
-            outside_epsilon_mask = outside_epsilon_mask |  \
-                                   ((abs(raw_diff) > (aDataObject.data * (float(epsilonPercent) / 100.0))) & valid_in_both)
+            outside_epsilon_mask |= (abs(raw_diff) > abs(aDataObject.data * (float(epsilonPercent) / 100.0))) & valid_in_both
         
         # trouble points = mismatched nans, mismatched missing-values, differences that are too large 
         trouble_pt_mask = ( (aDataObject.masks.non_finite_mask ^ bDataObject.masks.non_finite_mask) |