Re: [Matplotlib-users] barchart errorbars always in both directions

[Meesters, Aesku.K. I. <mee...@ae...>]

Thanks, Ben. This is indeed what I was looking for and gives the desired
behavior.

Thanks a lot!
Chris

On Wed, 2012-05-23 at 08:55 -0400, Benjamin Root wrote:
> 
> On Wed, May 23, 2012 at 4:03 AM, Meesters, Aesku.Kipp Institute
> <mee...@ae...> wrote:
>         Hi,
>         
>         I'm following the example in the gallery to do a barchart plot
>         (see
>         http://matplotlib.sourceforge.net/examples/api/barchart_demo.html ).
>         
>         In contrast to the example I would like to see the error bars
>         only above
>         the bars, so I tried
>         
>         rects2 = ax.bar(ind+width, womenMeans, width, color='y',
>                        yerr=stds, error_kw = {'barsabove': True,
>                                               'ecolor'   : 'k'}
>         
>         While the 'ecolor' argument gets accepted, 'barsabove'
>         apparently has no
>         effect (error bars still point up and downwards) - yet, no
>         warning /
>         error is triggered. Where is my mistake? Or is this a bug
>         (still using
>         version 1.0.1) with a known work-around?
>         
>         TIA
>         Chris
>         
> 
> Chris,
> 
> I don't think "barsabove" does what you want.  By "above", it means
> that the errorbar is plotted in a layer on top of the plotting symbol
> rather than in the layer under it.  Both ends will be plotted.
> 
> To get what you want, you might want to try (Note: untested):
> 
> rects2 = ax.bar(ind+width, womenMeans, width, color='y',
>                yerr=np.vstack([[0]*len(stds), stds]), error_kw =
> {'ecolor'   : 'k'})
> 
> When yerr is a 2xN numpy array, errorbars are plotted at y-yerr[0, :]
> and y+yerr[1,:]. So, np.vstack creates a 2xN array where the first row
> is all zeros and the second row is the stds values.
> 
> I hope that works for you!
> Ben Root
> 
>