Question

I was trying to draw a barchart using matplotlib.The number of items to be plotted can vary . I cannot set the figure.set_size_inches(w,h) or set_figwidth(w) with constants(like 6.,8. or 8.,12. etc),since I cannot tell in advance what the value of w or h should be.I want the width of figure to increase as the number of items to be plotted increases.Can someone tell me how I can do this?

import pylab

def create_barchart(map):
    xvaluenames = map.keys()
    xvaluenames.sort()
    yvalues = map.values()
    max_yvalue = get_max_yvalue(yvalues)
    xdata = range(len(xvaluenames))
    ydata = [map[x] for x in xvaluenames]
    splitxdata = [x.split('-',1) for x in xvaluenames]
    xlabels = [x[0] for x in splitxdata]
    figure = pylab.figure()
    ax = figure.add_subplot(1,1,1)
    figsize = figure.get_size_inches()
    print 'figure size1=',figsize,'width=',figsize[0],'height=',figsize[1]
    barwidth = .25
    ystep =  max_yvalue/5
    pylab.grid(True)
    if xdata and ydata:
        ax.bar(xdata, ydata, width=barwidth,align='center',color='orange')
        ax.set_xlabel('xvalues',color='green')
        ax.set_ylabel('yvalues',color='green')
        ax.set_xticks(xdata)
        ax.set_xlim([min(xdata) - 0.5, max(xdata) + 0.5])
        ax.set_xticklabels(xlabels)
        ax.set_yticks(range(0,max_yvalue+ystep,ystep))
        ax.set_ylim(0,max(ydata)+ystep)
    figure.autofmt_xdate(rotation=30)
    figure.savefig('mybarplot',format="png")
    print 'figure size2=',figure.get_size_inches()
    pylab.show()

def get_max_yvalue(yvals):
    return max(yvals) if yvals else 0

if I try with a small set of items,I get

if __name__=='__main__':
    datamap = dict(mark=39,jim=40, simon=20,dan=33)    
    print datamap
    create_barchart(datamap)

but if I use a larger set

datamap = dict(mark=39,jim=40, simon=20,dan=33) 
additional_values= dict(jon=34,ray=23,bert=45,kevin=35,ned=31,bran=11,tywin=56,tyrion=30,jaime=36,griffin=25,viserys=25)
datamap.update(additional_values)  
create_barchart(datamap)

This looks awful,
I am wondering if there is a way to increase the width of figure,according to the number of items to be plotted,keeping the width of bars in both cases same

Answer 1

You can set the width when you initialize the figure:

# default scale is 1 in your original case, scales with other cases:
widthscale = len(yvalues)/4 
figsize = (8*widthscale,6) # fig size in inches (width,height)
figure = pylab.figure(figsize = figsize) # set the figsize

Replace the figure = pylab.figure() line with the above three lines and you get what your asking for.