On Tue, Mar 20, 2012 at 4:10 PM, Daniel Hyams <dhy...@gmail.com> wrote:
> There was a request a while back to create plots that are more
> application-oriented for the matplotlib gallery, so I'd like to submit this
> one for inclusion. I tried to spruce it up a bit to show what MPL can do,
> and I'm sure that the folks here can improve upon it. But at any rate,
> this is a good first iteration I think.
>
> I'm also going to try to replace the plot at wikipedia (for the Moody
> diagram) with this one. The one at wikipedia is not quite correct in the
> way friction factors are computed, and a nice side effect is that mpl gets
> some exposure there as well (although there are probably dozens of mpl
> plots already there, but I don't know how to find them).
>
> The below is meant as constructive criticism; I certainly am committed to
> using matplotlib and offering patches here and there as I can; I would love
> to see wider adoption of it. I also concede that in the below items, I
> might have missed something obvious. I'm trying to approach this as a user
> who was just introduced to matplotlib, and had to create the plot that is
> attached.
>
> 1) The table mechanism, while very nice and useful, could use some
> improvement; it should be easier to specify alignment for the table cells,
> and individual fonts for each cell.
> 2) drawing the arrows was much harder than it needs to be. Better
> defaults for arrowhead sizes would help a lot (instead of them being
> hardcoded to certain numbers, have the defaults be fungible based on how
> long the arrow is in pixel space), and I had to resort to using the
> annotate() function to draw them, after spending over an hour trying to use
> plt.arrow(). plt.arrow() had some problems drawing arrowheads on log-log
> plots, and well as not supporting a double-ended arrow.
> 3) drawing the shading using polygons was great and easy.
> 4) the title by default is placed too close to the top
> 5) the plot axis labels were clipped by default; had to pull the axis
> limits in (I know, this is a longstanding thing, but a new user would
> wrinkle their nose)
>
> All in all, the plot took a lot longer to make than I had anticipated;
> mainly due to some fussing with the issues above until I found something
> that worked.
>
> Hope that you find the sample useful.
>
> --
> Daniel Hyams
> dhy...@gmail.com
>
I'm not one of the mpl-developers, so I can't speak about the likelihood of
inclusion, but I do think it's a great plot (esp. since my background is in
fluid mechanics). I think it'd be a great example to have, especially if
the gallery gets split up into different
categories<https://github.com/matplotlib/matplotlib/pull/714>.
(Personally,
I think it would be nice to have a category for complex, application-style
examples, and multiple categories for simplified-versions of most of the
current examples).
I agree with most of your points, but I don't have much to add on anything
except for #2: Drawing arrows has been painful for me as well. If I find
the time, I plan on putting together a PR which draws arrows using a
FancyArrowPatch and a Line2D object. Although, `annotate` works great for
it's designed purpose, it can be cumbersome for drawing simple arrows.
-Tony
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