Re: [Matplotlib-users] How to provide colorbars for scatterplots created this way?

[Steven B. <bo...@ph...>]

I normally just plot a whole bunch of arrays... and then add the color bar

sc1 = f1s1.scatter(array[:,0], array[:,1], c=array[:,2], s=50, 
cmap='spectral',edgecolor='w')
bar = pyl.colorbar(sc1)
bar.set_label("label")


Steven

On 12/20/12 5:54 PM, Paul Hobson wrote:
> On Thu, Dec 20, 2012 at 1:05 PM, Kynn Jones <ky...@gm... 
> <mailto:ky...@gm...>> wrote:
>
>     I create PNG files of scatterplots with code that, in essence,
>     goes as in the sketch below:
>
>
>     cmap = (matplotlib.color.LinearSegmentedColormap.
>             from_list('blueWhiteRed', ['blue', 'white', 'red']))
>
>     fig = matplotlib.figure.Figure(figsize=(4, 4), dpi=72)
>     ax = fig.gca()
>
>     for marker in 'o s ^ *'.split():
>
>         X, Y, COLOR = zip(*((record.x, record.y, record.level)
>                             for record in data if record.marker ==
>     marker))
>
>         ax.scatter(X, Y, marker=marker,
>          c=COLOR, vmin=0, vmax=1, cmap=cmap,
>                    **otherkwargs)
>
>     # various settings of ticks, labels, etc. omitted
>
>     canvas = matplotlib.backends.backend_agg.FigureCanvasAgg(fig)
>     fig.set_canvas(canvas)
>
>     # IMPORTANT: the generated figure is *not* displayed on the
>     screen, but
>     # rather it is output to disk as a PNG file:
>     canvas.print_png('/path/to/output/fig.png')
>
>
>
>     My question is this:
>
>     What do I need to add to the code above to get a vertical colorbar
>     (representing the colormap incmap) along the plot's right edge?
>
>     I word the question in this way because I am not sufficiently
>     facile with Matplotlib to deviate too far from the working code above.
>
>     In particular, my code *has* to be able to produce PNG files
>     *non-interactively*, so the last line in the code sketch above is
>     really essential.
>
>     Thanks in advance!
>
>     kj
>
>
> Can you provide some more information and a self-contained example? 
> What is your record object? Is it a pandas dataframe? Are the limits 
> of record.level consistent with vmax and vmin kwargs fed in the call 
> to ax.scatter?
>
> Typically you can just do:
>
> import matplotlib.pyplot as plt
> # blah blah
> fig, ax = plt.subplots()
> s = ax.scatter()...
> cb = plt.colorbar(s)
> cb.set_label('Cbar Label Here')
>
> Also, I don't think you need to mess with the backend stuff. Just do 
> fig.savefig('figname.png'). If you need separate markers for each set, 
> make a single call to scatter for each data group, and use numpy to 
> figure out what the appropriate vmax a vmin limits are for the colorbar.
>
> -paul
>
>
> ------------------------------------------------------------------------------
> LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial
> Remotely access PCs and mobile devices and provide instant support
> Improve your efficiency, and focus on delivering more value-add services
> Discover what IT Professionals Know. Rescue delivers
> http://p.sf.net/sfu/logmein_12329d2d
>
>
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users

-- 

Steven Boada

Doctoral Student
Dept of Physics and Astronomy
Texas A&M University
bo...@ph...