Work around a bug in pandas.DataFrame.replace to set the color

In the case a original value (e.g. 0-9A-F) was part of a color
defintion, using df.replace{dict} would do a double replace on the
same cell, resulting in colors like "#12345#ABCDEF", which would
then throw an error during plotting.

Using apply(lambda x: replacements[x]) is probably slower, so should
be replaced when the pandas bug is gone.

See pandas-dev/pandas#5338 for the bugreport
in pandas.

Author: jankatins

ggplot/ggplot.py

@@ -331,10 +331,15 @@ def _get_layers(self, data=None):
                     else:
                         color_mapping = {value: color.next() for value in possible_colors}
                     rev_color_mapping = {v: k for k, v in color_mapping.items()}
-                    mapping.color = mapping.color.replace(color_mapping)
+                    # replace does not work in some cases: https://github.com/pydata/pandas/issues/5338
+                    # "6" -> "#123456" would end up like "#12345#123456"
+                    # Use a workaround which is hopefully not too bad when we only have a few unique values
+                    #mapping.color = mapping.color.replace(color_mapping)
+                    mapping.color = mapping.color.apply(lambda x: color_mapping[x])
 
         rev_shape_mapping = {}
         if 'shape' in mapping:
+            #Todo: also look if the shapes are already useable like in the color case?
             possible_shapes = np.unique(mapping['shape'])
             shape = shapes.shape_gen()
             shape_mapping = {value: shape.next() for value in possible_shapes}
@@ -344,6 +349,7 @@ def _get_layers(self, data=None):
 
         rev_linetype_mapping = {}
         if 'linestyle' in mapping:
+            #Todo: also look if the linestyles are already useable like in the color case?
             mapping['linestyle'] = mapping['linestyle'].apply(str)
             possible_styles = np.unique(mapping['linestyle'])
             linestyle = linestyles.line_gen()