adding from_list to custom cmap tutorial

[choldgraf]

This PR adds a bit more explanation to the docstring for this tutorial, rearranges the data creation to be at the beginning, and adds a small section that shows how to create a colormap from a list of RGB tuples.

@NelleV WDYT?

[choldgraf]

Ah, and it creates this extra figure, illustrating the N parameter for from_list:

[choldgraf]

btw, let me know if you want me to change the other objects in this tutorial so they're object-based instead of plt. based. I think somebody mentioned they'd like to see that but don't know if it's worth it or not.

[NelleV]

I think the convention is as follow:

fig, axes = plt.subplots()

Maybe @mdboom or @tacaswell can confirm?
In any case, we should be as consistent as possible on the whole file. There are other places in this example that don't use the object oriented interface: do you mind editing those as well (for example l.170 to 182).

[choldgraf]

Cool - yep I can edit those as well (see my latest comment on the main thread).

[NelleV]

Great! Thanks.

[choldgraf]

It looks like the colorbar mapping is somewhat different when doing it object-oriented style. If I do im = imshow(... and then call fig.colorbar(im, cax=ax[0, 0]), etc, then it gives a plot like this:

I think the colorbars are super tiny in the corners. Know how I can fix this?

[efiring]

The cax kwarg takes an Axes that you have made yourself to hold the colorbar; I think what you want is the ax kwarg, which takes the parent Axes from which space for the colorbar will be taken.

[choldgraf]

hooray that worked!

On Tue, Jun 28, 2016 at 10:27 AM, Eric Firing notifications@github.com
wrote:

In examples/pylab_examples/custom_cmap.py
#6662 (comment):

+colors = [(1, 0, 0), (0, 1, 0), (0, 0, 1)] # R -> G -> B
+n_bins = [2, 5, 10, 100] # Discretizes the interpolation into bins
+cmap_name = 'my_list'
+f, axs = plt.subplots(1, 4, figsize=(10, 5))

The cax kwarg takes an Axes that you have made yourself to hold the
colorbar; I think what you want is the ax kwarg, which takes the parent
Axes from which space for the colorbar will be taken.

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[choldgraf]

(thx)

On Tue, Jun 28, 2016 at 10:29 AM, Chris Holdgraf choldgraf@gmail.com
wrote:

hooray that worked!

On Tue, Jun 28, 2016 at 10:27 AM, Eric Firing notifications@github.com
wrote:

In examples/pylab_examples/custom_cmap.py
#6662 (comment)
:

+colors = [(1, 0, 0), (0, 1, 0), (0, 0, 1)] # R -> G -> B
+n_bins = [2, 5, 10, 100] # Discretizes the interpolation into bins
+cmap_name = 'my_list'
+f, axs = plt.subplots(1, 4, figsize=(10, 5))

The cax kwarg takes an Axes that you have made yourself to hold the
colorbar; I think what you want is the ax kwarg, which takes the parent
Axes from which space for the colorbar will be taken.

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[NelleV]

Hi Chris,

Thanks for the patch! I think the additional documentation is great.
Have you tried building the sphinx documentation? If so, do you mind adding an image of how this example page looks on the pull request?

Thanks,
Nelle

[choldgraf]

I'll try building sphinx after updating the commit. Can you give a quick reminder on how to do this, it's been a while since I've built docs

[choldgraf]

Actually it's just python ./doc/make.py html isn't it? I'm getting a weird error about latex_math already being registered. Do you know if there's a way to throw warnings for something like that instead of erroring?

[efiring]

Use the --allowsphinxwarnings option to make.py.

[NelleV]

@efiring this is IMO a bit annoying. If we used the "newer" build system of sphinx, that would not happen. I can easily create a PR with the new Makefile (and make.bat) files. Would that be of any interest to the project?

[jenshnielsen]

That warning is caused by Sphinx 1.4x being stricter And already fixed on current master. The easiest way to suppress it rather than allowing it is to either rebase on current master or downgrade Sphinx to 1.3x

[jenshnielsen]

@NelleV Setting warningsaserrors as the default is done very much on purpose and as the person that fixed more than 800 Sphinx warnings before that became possible I would be very hard to convince to change this. Travis builds the docs every a branch is pushed with warnings as errors and it works just fine

[jenshnielsen]

This is the PR that fixes it #6238 which was merged a few days after Sphinx 1.4 was released

[NelleV]

@jenshnielsen I'm running the latest matplotlib, and I still have this problem while using make.py.

[jenshnielsen]

Sorry I misunderstood I thought you wanted to change to Makefiles to get rid of the warningsaserrors

It's puzzling that you still see this error since travis builds without that warning and has done for a long time

[NelleV]

In any case, the make.py file is antiquated. The new version of the matplotlib build would not have required the patch from #6238 . The problem with make.py is that it does not guet updated with the library, but it should. Hence the move from generating the make.py to a makefile that calls itself the sphinx-build executable.

[jenshnielsen]

Im happy to convert to Makefiles as long as we build the docs with warningsaserrors

[choldgraf]

ah thanks for that - sphinx is building now w/ the flag...gonna take a bit of time for it to finish, I'll update when that's done

[NelleV]

@jenshnielsen I don't think it makes sense to activate the -W option if we have to disable it to have the documentation build… It is what is happening right now. It doesn't bring any advantages, and has the strong disaventages of increasing the difficulty of building the documentation, and thus of contributing to matplotlib.

[jenshnielsen]

It at the very least need to be the enabled on Travis as I said I had to fix more than 800 warnings including very significant wrongly rendered pages that went unnoticed for years. Since we made this the default on travis we have caught a large number of pr's with invalid RST syntax which would have been unnoticed and only fixed years later. We can change the default and make this optional again i.e. revert 1af4ca0

[choldgraf]

Here's how it looks in the docs:

[NelleV]

That looks good to me. I don't really understand why the appveyor build fails, and I don't think it has anything to do with your PR.

Thanks for the patch!

[choldgraf]

Yeah I couldn't figure that one out either...but didn't seem related. Let
me know if there's anything else you'd like me to do!

Chris

On Tue, Jun 28, 2016 at 10:55 PM, Nelle Varoquaux notifications@github.com
wrote:

That looks good to me. I don't really understand why the appveyor build
fails, and I don't think it has anything to do with your PR.

Thanks for the patch!

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[jenshnielsen]

appveyor have some issues at the moment #6520 is work towards resolving it

[tacaswell]

Thanks!

backported to v1.5.x as 9e5b18a

[choldgraf]

🎉 🎉 🎉