[Doc] add pcolor and contour to tutorials/introductory/sample_plots.py - #9387

fwiw (not directly related but perhaps you can also remove it here) there seems to be an extraneous plot at the bottom of the page, see below http://matplotlib.org/devdocs/tutorials/introductory/sample_plots.html#xkcd-style-sketch-plots

Well, it does get used for the thumbnail. But can I choose one of the other plots for the thumbnail?

I'll just leave it, but include a section heading and bit of commentary so it doesn't look so mysterious. There is probably a way to suppress the code as well, but it does't hurt anything....

Ah... looks like a feature (pick a thumbnail not in the notebook) we should ask the s-g gallery folks about (I think it's a nice thumbnail). @choldgraf ? :-)

Also, there's no imshow example, which seems waaay more fundamental. Perhaps something like:

The imshow() function (I'd replace "command" by "function" throughout, we're not MATLAB...) can be used to make a colored representation of a 2D array.
(example)
If the underlying array uses irregular sampling, consider using pcolormesh()
(example)
Contour plots, created by contour() and contourf(), are yet another way to represent 2D data.
(example)

OK, I can do that. I thought I was being good and economical by choosing an example that had pcolor and contour in one figure, but I'm happy to add a few more examples.

(I was pretty surprised that none of these functions made it onto the "sample plots" page, since they are the main type of visualization I do - even more fundamental than line plots)

It's all a matter of field of application I guess... (typically imshow is enough for me :-))

Ooops, made git mistake. Closing and re-opening.

@jklymak git push --force / git push --force-with-lease should let you reuse the same PR. At least I tend to use it quite liberally (on PRs only of course).

Ahhh. I should have done that! Thanks.