Merge pull request matplotlib#19467 from anntzer/v

Shorten the implementation of violin().

Author: efiring

lib/matplotlib/axes/_axes.py

@@ -8106,18 +8106,18 @@ def violin(self, vpstats, positions=None, vert=True, widths=0.5,
           - ``cquantiles``: A `~.collections.LineCollection` instance created
             to identify the quantiles values of each of the violin's
             distribution.
-
         """
 
         # Statistical quantities to be plotted on the violins
         means = []
         mins = []
         maxes = []
         medians = []
-        quantiles = np.asarray([])
+        quantiles = []
+
+        qlens = []  # Number of quantiles in each dataset.
 
-        # Collections to be returned
-        artists = {}
+        artists = {}  # Collections to be returned
 
         N = len(vpstats)
         datashape_message = ("List of violinplot statistics and `{0}` "
@@ -8135,84 +8135,56 @@ def violin(self, vpstats, positions=None, vert=True, widths=0.5,
         elif len(widths) != N:
             raise ValueError(datashape_message.format("widths"))
 
-        # Calculate ranges for statistics lines
-        pmins = -0.25 * np.array(widths) + positions
-        pmaxes = 0.25 * np.array(widths) + positions
+        # Calculate ranges for statistics lines (shape (2, N)).
+        line_ends = [[-0.25], [0.25]] * np.array(widths) + positions
+
+        # Colors.
+        if rcParams['_internal.classic_mode']:
+            fillcolor = 'y'
+            linecolor = 'r'
+        else:
+            fillcolor = linecolor = self._get_lines.get_next_color()
 
         # Check whether we are rendering vertically or horizontally
         if vert:
             fill = self.fill_betweenx
-            perp_lines = self.hlines
-            par_lines = self.vlines
+            perp_lines = functools.partial(self.hlines, colors=linecolor)
+            par_lines = functools.partial(self.vlines, colors=linecolor)
         else:
             fill = self.fill_between
-            perp_lines = self.vlines
-            par_lines = self.hlines
-
-        if rcParams['_internal.classic_mode']:
-            fillcolor = 'y'
-            edgecolor = 'r'
-        else:
-            fillcolor = edgecolor = self._get_lines.get_next_color()
+            perp_lines = functools.partial(self.vlines, colors=linecolor)
+            par_lines = functools.partial(self.hlines, colors=linecolor)
 
         # Render violins
         bodies = []
         for stats, pos, width in zip(vpstats, positions, widths):
-            # The 0.5 factor reflects the fact that we plot from v-p to
-            # v+p
+            # The 0.5 factor reflects the fact that we plot from v-p to v+p.
             vals = np.array(stats['vals'])
             vals = 0.5 * width * vals / vals.max()
-            bodies += [fill(stats['coords'],
-                            -vals + pos,
-                            vals + pos,
-                            facecolor=fillcolor,
-                            alpha=0.3)]
+            bodies += [fill(stats['coords'], -vals + pos, vals + pos,
+                            facecolor=fillcolor, alpha=0.3)]
             means.append(stats['mean'])
             mins.append(stats['min'])
             maxes.append(stats['max'])
             medians.append(stats['median'])
-            q = stats.get('quantiles')
-            if q is not None:
-                # If exist key quantiles, assume it's a list of floats
-                quantiles = np.concatenate((quantiles, q))
+            q = stats.get('quantiles')  # a list of floats, or None
+            if q is None:
+                q = []
+            quantiles.extend(q)
+            qlens.append(len(q))
         artists['bodies'] = bodies
 
-        # Render means
-        if showmeans:
-            artists['cmeans'] = perp_lines(means, pmins, pmaxes,
-                                           colors=edgecolor)
-
-        # Render extrema
-        if showextrema:
-            artists['cmaxes'] = perp_lines(maxes, pmins, pmaxes,
-                                           colors=edgecolor)
-            artists['cmins'] = perp_lines(mins, pmins, pmaxes,
-                                          colors=edgecolor)
-            artists['cbars'] = par_lines(positions, mins, maxes,
-                                         colors=edgecolor)
-
-        # Render medians
-        if showmedians:
-            artists['cmedians'] = perp_lines(medians,
-                                             pmins,
-                                             pmaxes,
-                                             colors=edgecolor)
-
-        # Render quantile values
-        if quantiles.size > 0:
-            # Recalculate ranges for statistics lines for quantiles.
-            # ppmins are the left end of quantiles lines
-            ppmins = np.asarray([])
-            # pmaxes are the right end of quantiles lines
-            ppmaxs = np.asarray([])
-            for stats, cmin, cmax in zip(vpstats, pmins, pmaxes):
-                q = stats.get('quantiles')
-                if q is not None:
-                    ppmins = np.concatenate((ppmins, [cmin] * np.size(q)))
-                    ppmaxs = np.concatenate((ppmaxs, [cmax] * np.size(q)))
-            # Start rendering
-            artists['cquantiles'] = perp_lines(quantiles, ppmins, ppmaxs,
-                                               colors=edgecolor)
+        if showmeans:  # Render means
+            artists['cmeans'] = perp_lines(means, *line_ends)
+        if showextrema:  # Render extrema
+            artists['cmaxes'] = perp_lines(maxes, *line_ends)
+            artists['cmins'] = perp_lines(mins, *line_ends)
+            artists['cbars'] = par_lines(positions, mins, maxes)
+        if showmedians:  # Render medians
+            artists['cmedians'] = perp_lines(medians, *line_ends)
+        if quantiles:  # Render quantiles: each width is repeated qlen times.
+            artists['cquantiles'] = perp_lines(
+                quantiles, *np.repeat(line_ends, qlens, axis=1))
 
         return artists