Fixed GeoArray.show_histogram() (issue #17).

geoarray/baseclasses.py

@@ -1333,10 +1333,10 @@ class GeoArray(object):
         """
 
         if self.nodata is not None and exclude_nodata:
-            data = np.ma.masked_equal(self[band], self.nodata)
+            data = np.ma.masked_equal(self[band] if not self.bands == 1 else self[:], self.nodata)
             data = data.compressed()
         else:
-            data = self[band]
+            data = self[band] if not self.bands == 1 else self[:]
 
         vmin = vmin if vmin is not None else np.nanpercentile(data, 1)
         vmax = vmax if vmax is not None else np.nanpercentile(data, 99)