add plabel, vlabel arguments to export.triplot

This patch adds the plabel and vlabel arguments to export.triplot for
the coordinates and values, respectively. For 1D plots the labels are
used for the x and y axes; for 2D plots the plabel is used for both x
and y and the vlabel is used for the colorbar.

nutils/export.py

@@ -60,12 +60,12 @@ def plotlines_(ax, xy, lines, **kwargs):
   ax.add_collection(lc)
   return lc
 
-def triplot(name, points, values=None, *, tri=None, hull=None, cmap=None, clim=None, linewidth=.1, linecolor='k'):
+def triplot(name, points, values=None, *, tri=None, hull=None, cmap=None, clim=None, linewidth=.1, linecolor='k', plabel=None, vlabel=None):
   if (tri is None) != (values is None):
     raise Exception('tri and values can only be specified jointly')
   with mplfigure(name) as fig:
     if points.shape[1] == 1:
-      ax = fig.add_subplot(111)
+      ax = fig.add_subplot(111, xlabel=plabel, ylabel=vlabel)
       if tri is not None:
         plotlines_(ax, [points[:,0], values], tri)
       if hull is not None:
@@ -77,12 +77,12 @@ def triplot(name, points, values=None, *, tri=None, hull=None, cmap=None, clim=N
       else:
         ax.set_ylim(clim)
     elif points.shape[1] == 2:
-      ax = fig.add_subplot(111, aspect='equal')
+      ax = fig.add_subplot(111, xlabel=plabel, ylabel=plabel, aspect='equal')
       if tri is not None:
         im = ax.tripcolor(*points.T, tri, values, shading='gouraud', cmap=cmap, rasterized=True)
         if clim is not None:
           im.set_clim(clim)
-        fig.colorbar(im)
+        fig.colorbar(im, label=vlabel)
       if hull is not None:
         plotlines_(ax, points.T, hull, colors=linecolor, linewidths=linewidth, alpha=1 if tri is None else .5)
       ax.autoscale(enable=True, axis='both', tight=True)