Use scale.name parameter for the axis-title

This is inline with the documentation, it was simply ignored for
the position scales. Other scales were not affected.

fixes #105

Author: has2k1

doc/changelog.rst

@@ -44,6 +44,10 @@ Bug Fixes
   :class:`~plotnine.stats.stat_bin_2d` to properly handle the
   ``breaks`` parameter when used with a transforming scale.
 
+- Fixed issue with x and y scales where the ``name`` of the scale was
+  ignored when determining the axis titles. Now, the ``name`` parameter
+  is specified, it is used as the title. (:issue:`105`)
+
 v0.3.0
 ------
 *(2017-11-08)*

plotnine/facets/layout.py

@@ -202,3 +202,37 @@ def check_layout(self):
             raise PlotnineError(
                 "Facet layout has bad format. It must contain "
                 "the columns '{}'".format(required))
+
+    def xlabel(self, labels):
+        """
+        Determine x-axis label
+
+        Parameters
+        ----------
+        labels : dict
+            Labels as specified by the user through the ``labs`` or
+            ``xlab`` calls.
+
+        Returns
+        -------
+        out : str
+            x-axis label
+        """
+        return self.panel_scales_x[0].name or labels.get('x', '')
+
+    def ylabel(self, labels):
+        """
+        Determine x-axis label
+
+        Parameters
+        ----------
+        labels : dict
+            Labels as specified by the user through the ``labs`` or
+            ``ylab`` calls.
+
+        Returns
+        -------
+        out : str
+            y-axis label
+        """
+        return self.panel_scales_y[0].name or labels.get('y', '')

plotnine/ggplot.py

@@ -498,9 +498,10 @@ def _draw_labels(self):
 
         # Get the axis labels (default or specified by user)
         # and let the coordinate modify them e.g. flip
-        labels = self.coordinates.labels(
-            {'x': self.labels.get('x', ''),
-             'y': self.labels.get('y', '')})
+        labels = self.coordinates.labels({
+            'x': self.layout.xlabel(self.labels),
+            'y': self.layout.ylabel(self.labels)
+        })
 
         # The first axes object is on left, and the last axes object
         # is at the bottom. We change the transform so that the relevant