[Matplotlib-users] Bar chart corruption when plotting multiple subplots in MATPLOTLIB

[p.bingham <p.b...@ke...>]

I've created a class that allows a user to add several charts to a MATPLOTLIB
window. These can be either a line chart or a bar chart. It also has the
feature that when a chart has already been added to the window (as
identified from rowID) rather than draw a new plot it will replace the data
in the old plot. ie it allows for updates (animation) 

This works grand for the line plot but I get corruption when plotting
several bar charts. The class looks like:

  import math

  class TFrmPlot():

    def __init__(self, point_lists, deleteCallback, plotType, rowID):                    
            import matplotlib 
            matplotlib.interactive( True )
            matplotlib.use( 'WXAgg' )  

            import matplotlib.pyplot as plt
            self.plt = plt
            self.fig = plt.figure()      
            self.fig.canvas.mpl_connect('close_event', self.on_close)    

            import matplotlib.axes as ax    
            self.ax = ax

            self.deleteCallback = deleteCallback
            self.chartArray = []              
            self.addChart(point_lists, plotType, rowID)

        def close(self):    
            self.plt.close('all')
            #self.fig.close()

        def replaceChartDataIfChartExists(self, point_lists, rowID):
            if rowID==0:
                pass
            for chart in self.chartArray:
                for plot in chart.plots:
                    if plot.rowID == rowID:
                        plot.points = point_lists                               
                        if plot.plotType=="Point":                         
                           
plot.plotItem.set_data(point_lists[0],point_lists[1])                          
                            chart.subPlot.draw_artist(plot.plotItem)                        
                            self.fig.canvas.blit(chart.subPlot.bbox) 
                        else:                      
                            for rect, h in zip(plot.plotItem,
point_lists[1]):
                                rect.set_height(h)   
                        chart.subPlot.relim()                     
                        chart.subPlot.autoscale_view(True,True,True)                                                       
                        self.plt.draw()
                        return True
            return False    

        def addChart(self, point_lists, plotType, rowID):
            self.chartArray.append(TChart(rowID,plotType,point_lists))
            self._drawAll() 

        def addPlot(self, point_lists, plotType, rowID):           
            chartNum = len(self.chartArray)
           
self.chartArray[chartNum-1].plots.append(TPlot(rowID,plotType,point_lists))  
            self._drawAll()

        def on_close(self, event):
            self.deleteCallback()

        def _drawAll(self):     
            self.plt.clf()
            numSubPlots = len(self.chartArray)
            numCols = self._noCols(numSubPlots)
            IndexConverter = TIndexConverter(numCols)
            subPlot = None
            for chartIndex in range(0,numSubPlots):
                if numSubPlots==1:                
                    subPlot = self.fig.add_subplot(1,1,1)
                elif numSubPlots==2:                             
                    subPlot = self.fig.add_subplot(1,2,chartIndex+1)
                else:
                    subPlot =
self.fig.add_subplot(2,numCols,IndexConverter._getSubPlotIndex(chartIndex))
                subPlot.relim()           
                subPlot.autoscale_view(True,True,True)
                self.chartArray[chartIndex].subPlot = subPlot
                self._drawSubs(self.chartArray[chartIndex])                   
            self.plt.show() 

        def _drawSubs(self, chart):
            for plot in chart.plots:
                if plot.plotType=="Point":          
                    chart.subPlot.plot(plot.points[0],plot.points[1])
                    plot.plotItem =
chart.subPlot.lines[len(chart.subPlot.lines)-1]
                else:
                    kwargs = {"alpha":0.5}
                    plot.plotItem =
chart.subPlot.bar(plot.points[0],plot.points[1],
width=self._calculateleastDiff(plot.points[0]), **kwargs)     

        def _noCols(self, numSubPlots):
            return math.ceil(float(numSubPlots)/2.0)  

        def _calculateleastDiff(self, xValues):
            xValues2 = sorted(xValues)
            leastDiff = None
            lastValue = None
            for value in xValues2:
                if lastValue is not None: 
                    diff = value-lastValue            
                    if leastDiff is None or diff < leastDiff:
                        leastDiff = diff
                lastValue = value 
            return leastDiff

This is a bit long so to summarise:

addChart -- basically adds a new subplot

addPlot -- adds a new line or bar to an existing subplot

replaceChartDataIfChartExists -- refreshes the data if the ID already exists

The dummy data that I'm using just plots a positive gradient and a negative
gradient line in succession. My plots however can get into a state where
one/some or all of the bar plots become corrupted. It looks almost like the
x/y axis has been rotated, with the individual bars not starting from the
x-axis. The issue is intermittent; sometimes I will get several plots as
expected. Once a plot becomes corrupted all future updates remain corrupted.

Corrupted Chart:
<http://matplotlib.1069221.n5.nabble.com/file/n40023/corrupted.png> 



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