Re: [Matplotlib-users] Horizontal bar chart with log x-axis, no filled boxes

[Tony Yu <ts...@gm...>]

On Thu, Jan 12, 2012 at 11:39 AM, Christophe Pettus <xo...@th...>wrote:

>
> On Jan 12, 2012, at 7:38 AM, Benjamin Root wrote:
> > Does everything work correctly if it is vertical?  In other words, use
> bar() and set the y-axis to log scale? An example script would be useful.
>
> No, it doesn't appear to work as a vertical bar chart, either.
>
> I've attached a test case below.  The results I get running it with the
> X-axis as log are:
>
>        http://thebuild.com/matlabtest/matlabtest-log.pdf
>
> Commenting out the call to ax.set_xscale('log') gives me:
>
>        http://thebuild.com/matlabtest/matlabtest.pdf
>
> Thanks!
>
> --
>
> import numpy as np
> import matplotlib
> from matplotlib.font_manager import FontProperties
>
> import random
>
> matplotlib.use('PDF')
>
> import matplotlib.pyplot as plot
>
> small_font = FontProperties()
> small_font.set_size('xx-small')
>
> ind = np.arange(20)
>
> label = [ str(r) for r in ind ]
> data1 = [ float(random.random()*100000000) for r in ind ]
> data2 = [ float(random.random()*100000000) for r in ind ]
>
> width = 0.25
>
> fig = plot.figure()
> ax = fig.add_subplot(111)
>
> ax.set_title('Table Title')
> ax.set_xlabel('X Label')
>
> ax.barh(ind, data1, width, linewidth=0, color='blue')
> ax.barh(ind, data2, width, left=data1, linewidth=0, color='yellow')
> ax.set_yticks(ind + width/2)
> ax.set_yticklabels(label, fontproperties=small_font)
> ax.set_xscale('log')
>
> plot.savefig('matlabtest-log.pdf')
>
> --
> -- Christophe Pettus
>

Isn't this just because zero isn't defined in log scale? The second set of
data plots fine because it doesn't start at zero, but it isn't obvious what
to do with the first set of data. If you just want to make this work, you
can set the left parameter of the first `barh` call to some constant; for
example:

>>> origin = 10**np.floor(np.log10(np.min(data1)))
>>> ax.barh(ind, data1, width, left=origin, linewidth=0, color='blue')

-Tony