Matplotlib双条形图：条形绘制不正确

Question

I am trying to plot two different data columns of a frame ("n" and "m") for each data set as two differently colored bars next to each other.

def graphPlot(data, size=None):
    pos = arange(len(data))+.5    # the bar centers on the y axis
    figure(figsize=size)
    xscale("log")
    barh(pos, data["n"], align='center', height=0.25, color="darkgrey")    
    barh(pos - 0.25, data["m"], align='center', height=0.25, color="lightblue")    
    yticks(pos, data["graph"])
    xlabel("")
    grid(True)

But it turns out like this:

Why are the bars not properly drawn? Are my position values wrong?

Answer 1

It's your xscale("log") call causing the problems. You need the plots to be scaled so instead pass log=True to the barh calls:

def graphPlot(data, size=None):
    pos = arange(len(data))+.5    # the bar centers on the y axis
    figure(figsize=size)
    #xscale("log")
    barh(pos, data["n"], align='center', height=0.25, color="darkgrey", log=True)    
    barh(pos - 0.25, data["m"], align='center', height=0.25, color="lightblue", log=True)    
    yticks(pos, data["graph"])
    xlabel("")
    grid(True)

An alternative is to use a pandas dataframe to hold your data and then simply call df[['ser1', 'ser2']].plot(kind='barh', logx=True) .