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

[Kynn J. <ky...@gm...>]

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