Re: [matplotlib-devel] [Matplotlib-users] ANN: mpltools 0.1 release

[Benjamin R. <ben...@ou...>]

On Fri, Jul 13, 2012 at 7:01 PM, Damon McDougall
<dam...@gm...>wrote:

> On Wed, Jul 11, 2012 at 08:33:21PM -0400, Tony Yu wrote:
> > On Wed, Jul 11, 2012 at 2:28 PM, Benjamin Root <ben...@ou...> wrote:
> >
> > >
> > >
> > > On Wed, Jul 11, 2012 at 11:23 AM, John Hunter <jd...@gm...>
> wrote:
> > >
> > >>
> > >>
> > >> On Wed, Jul 11, 2012 at 10:09 AM, Damon McDougall <
> > >> dam...@gm...> wrote:
> > >>>
> > >>> Well, as Ben said, that error fill plot is neato! It doesn't look too
> > >>> complicated, either. I'd be more than happy to port it over later
> today
> > >>> when I get bored of typing up my thesis. It'll probably only take me
> > >>> about 30 minutes.
> > >>>
> > >>> If nobody is opposed to this idea, I'll go ahead and submit a PR this
> > >>> evening (British Summer (hah!) Time).
> > >>>
> > >>
> > >>
> > >> While it is a nice graph, I am not sure that the use case is common
> > >> enough to justify a new plotting method.  One can get the same result
> with:
> > >>
> > >>
> > >>   In [68]: x = np.linspace(0, 2 * np.pi)
> > >>
> > >>   In [69]: y_sin = np.sin(x)
> > >>
> > >>   In [70]: err = np.concatenate([y_sin + 0.2, y_sin[::-1] - 0.2])
> > >>
> > >>   In [71]: plot(x, y_sin)
> > >>   Out[71]: [<matplotlib.lines.Line2D object at 0x96959ec>]
> > >>
> > >>   In [72]: fill_between(np.concatenate([x, x[::-1]]), err,
> > >> facecolor='red', alpha=0.5)
> > >>   Out[72]: <matplotlib.collections.PolyCollection object at 0x962758c>
> > >>
> > >> Admittedly the [::-1] thing is a bit counter-intuitive, but rather
> than
> > >> adding a new plotting method, perhaps we would be better off with a
> helper
> > >> method to create the xs and ys for fill_between
> > >>
> > >>   xs, ys = mlab.pad_line(x, y, 0.2)
> > >>   fill_between(xs, ys)
> > >>
> > >> JDH
> > >>
> > >
> > >
> > > I could definitely agree with a pad_line() function.  We might want to
> > > revisit the issue of how much visibility the mlab module should get in
> the
> > > documentation (it currently doesn't get much at all).  My whole take on
> > > mlab was that it was a left-over from the days of working around
> issues in
> > > NumPy and SciPy and that it was being slowly phased out.  As for other
> > > possible locations, cbook feels like it is more for the devs than for
> the
> > > users, and adding it to pyplot would render the whole purpose of
> creating
> > > this function as opposed to errorfill moot.
> > >
> > > As an additional point about such a pad_line function, it should
> probably
> > > be nice to mirror the errorbar() functionality to allow not only a
> constant
> > > error, but also a N, Nx1, or 2xN array of +/- error. (note that
> errorbar()
> > > for the 2xN array case does -row1 and +row2).
> > >
> >
> > Damon: it sounds like you're volunteering to submit a PR to add this
> > function ;)
> >
> > Here's the relevant bit (which should already handle the cases Ben
> mentions
> > above):
> >
> >
> >
> https://github.com/tonysyu/mpltools/blob/master/mpltools/special/errorfill.py#L54
> >
>
> Great. I've basically done this. I have one suggestion, though. In the
> case where len(zerr) == 2, you are setting
>
> zmin, zmax = zerr
>
> I think it makes more sense to set
>
> zmin, zmax = z - zerr[0], z + zerr[1]
>
> What do you think?
>

Your suggestion would be consistent with how errorbar() works, I think.

Ben Root