init object from existing pyplot object, replaced deprecated as_matrix()

classical/pandasplot.py

 """ utility classes to create xy plots and bar charts with pandas """
-import itertools
+from itertools import cycle
 import pandas as pd
 import matplotlib
 matplotlib.use('Qt5Cairo')
@@ -8,16 +8,23 @@ import matplotlib.pyplot as plt
 class PandasPlot:
     """ create xy plots and bar charts from a pandas DataFrame """
 
-    def __init__(self, df, showx=None, showy=None, labels=None, ptype='xyplot'):
-        fig = plt.figure()
-        self.plotobj = fig.add_subplot(111)
-        self.plotobj.set_xlabel(labels[showx])
-        self.plotobj.set_ylabel(labels[showy])
+    color_defs = ['b', 'g', 'r', 'c', 'm', 'y', 'k']
+
+    def __init__(self, df, showx=None, showy=None, labels=None,
+                 ptype='xyplot', plotobj=None, colors=None):
+        if plotobj is None:
+            fig = plt.figure()
+            self.plotobj = fig.add_subplot(111)
+            self.plotobj.set_xlabel(labels[showx])
+            self.plotobj.set_ylabel(labels[showy])
+        else:
+            self.plotobj = plotobj
         self.df = df
         self.showx = showx
         self.showy = showy
         self.labels = labels
         self.ptype = ptype
+        self.colors = cycle(self.color_defs) if colors is None else colors
 
     @classmethod
     def from_file(cls, filename, **kwargs):
@@ -27,9 +34,6 @@ class PandasPlot:
     def add_datasets(self, select=None, vary=None, marker='o'):
         """ add selected datasets from a dataframe to a plot object """
 
-        color_defs = ['b', 'g', 'r', 'c', 'm', 'y', 'k']
-        colors = itertools.cycle(color_defs)
-
         sel = True
         labs = []
         for key in select:
@@ -43,16 +47,18 @@ class PandasPlot:
                 self.barwidth = 0.5/self.nbars
             for numb, val in enumerate(vary[key]):
                 df2 = self.df[sel & (self.df[key] == val)].sort_values(self.showx)
-                xdata = df2[self.showx].as_matrix()
-                ydata = df2[self.showy].as_matrix()
+                xdata = df2[self.showx].values
+                ydata = df2[self.showy].values
+                if len(ydata) == 0:
+                    continue
                 legtx = ', '.join(labs) +', '+self.labels[key]+': '+str(val)
                 if self.ptype == 'xyplot':
                     self.plotobj.plot(xdata, ydata, marker=marker,
-                                      c=next(colors), linestyle='-',
+                                      c=next(self.colors), linestyle='-',
                                       label=legtx)
                 elif self.ptype == 'barchart':
                     self.plotobj.bar(xdata+0.5*numb/self.nbars, ydata,
-                                     self.barwidth, color=next(colors),
+                                     self.barwidth, color=next(self.colors),
                                      label=legtx)
 
     def show(self, legend=False):