Contouring handles nans in Z via masking.

efiring · efiring · commit e6ee8fb2c5b2 · 2009-03-25T19:27:28.000Z
(The bug in filled contouring with internal masked regions
remains.)

svn path=/trunk/matplotlib/; revision=7005
diff --git a/CHANGELOG b/CHANGELOG
@@ -1,5 +1,7 @@
-2009-03-20 Add AuxTransformBox in offsetbox.py to support some transformation. 
-           anchored_text.py example is enhanced and renamed 
+2009-03-25 Make contour and contourf handle nan in their Z argument. - EF
+
+2009-03-20 Add AuxTransformBox in offsetbox.py to support some transformation.
+           anchored_text.py example is enhanced and renamed
            (anchored_artists.py). - JJL
 
 2009-03-20 Add "bar" connection style for annotation - JJL
diff --git a/examples/pylab_examples/contourf_demo.py b/examples/pylab_examples/contourf_demo.py
@@ -3,7 +3,9 @@
 origin = 'lower'
 #origin = 'upper'
 
-test_masking = False  # There is a bug in filled contour masking.
+# The following controls only interior masking.
+test_masking = False  # There is a bug in filled contour masking with
+                      # interior masks.
 
 if test_masking:
     # Use a coarse grid so only a few masked points are needed.
@@ -30,6 +32,18 @@
     Z[0,0] = 0
     Z = ma.array(Z, mask=badmask)
 
+nr, nc = Z.shape
+
+# put NaNs in one corner:
+Z[-nr//6:, -nc//6:] = nan
+# contourf will convert these to masked
+
+
+Z = ma.array(Z)
+# mask another corner:
+Z[:nr//6, :nc//6] = ma.masked
+
+
 # We are using automatic selection of contour levels;
 # this is usually not such a good idea, because they don't
 # occur on nice boundaries, but we do it here for purposes
@@ -48,7 +62,7 @@
                         origin=origin,
                         hold='on')
 
-title('Nonsense')
+title('Nonsense (with 2 masked corners)')
 xlabel('word length anomaly')
 ylabel('sentence length anomaly')
 
@@ -72,7 +86,7 @@
                        colors = ('k',),
                        linewidths = (3,),
                        origin = origin)
-title('Listed colors')
+title('Listed colors (with 2 masked corners)')
 clabel(CS4, fmt = '%2.1f', colors = 'w', fontsize=14)
 colorbar(CS3)
 
diff --git a/lib/matplotlib/contour.py b/lib/matplotlib/contour.py
@@ -756,6 +756,7 @@ def _contour_args(self, *args):
             x,y,z = self._check_xyz(args[:3])
         else:
             raise TypeError("Too many arguments to %s; see help(%s)" % (fn,fn))
+        z = ma.masked_invalid(z, copy=False)
         self.zmax = ma.maximum(z)
         self.zmin = ma.minimum(z)
         if self.logscale and self.zmin <= 0:
