Re: [matplotlib-devel] Stacked plotting in matplotlib

[Nic E. <ns...@co...>]

Oops, sorry. I realized it was actually Ben Root who suggested I start this
discussion. Don't want to put words in anyones mouth.

Nic

On Sun, Aug 12, 2012 at 11:51 PM, Nic Eggert <ns...@co...> wrote:

> Hi all,
>
> I'd like to bring up a question spurred by PRs #847(mine) and #819
> (recently accepted). These PRs both deal with stacked plots. #819 adds the
> stackplot function to axes.py as a new function, which plots different 2-d
> datasets stacked atop each other. #847 slightly modifies the functioning of
> `hist` in axes.py by adding a new kwarg which allows datasets to be
> stacked. Currently this is only possible using the `barstacked` histtype.
> #847 makes it also work with the `step` and `stepfilled` histtypes.
>
> One of the issues that has been raised in the comments of #847 is whether
> we want to take this opportunity to come up with a unified way to handle
> "stacked-ness". Michael Droettboom suggested I raise this issue on this
> list. So far, there are 3 different approaches:
>
> 1. The state before #819. AFAIK the only way to do any sort of stacking
> was to call `hist` with `histtype="barstacked"`. This treats stacked
> histograms as a different type of histogram than non-stacked histograms.
> One of my motivations for writing #847 was to get stacked step and
> stepfilled histograms, which would require adding several new histtypes
> (stepstacked and stepfilledstacked). It seems to me that histtype mostly
> controls the style of the histogram plotted, and shouldn't have anything to
> do with "stacked-ness", so I think this is kind of clunky.
>
> 2. The approach I take in #847. Add a new kwarg which controls whether or
> not multiple datasets are stacked. I think this is the cleanest
> implementation, although that's probably obvious because it's how I wrote
> my PR. To keep everything consistent in this approach, we should remove the
> stackplot function added in #819, and move that functionality to the `plot`
> function, adding a `stacked` kwarg there.
>
> 3. The approach of #819. With this approach, we would add a separate
> function to handle stacked versions of different plots. I'd re-write #847
> as a new function called `stackhist`. This approach, IMO, doesn't scale
> well if we want to add "stacked-ness" to more plot types in the future.
>
> Please take a look at this and send comments about these proposals or any
> others you might have. I hope the community can come to a consensus which
> unifies the handling of stacked-ness.
>
> Whatever we end up choosing, I think adding a stacked step histogram will
> make it much easier to promote the use of mpl in high energy physics, where
> we use this style of plot frequently.
>
> Thanks,
>
> Nic Eggert
> Graduate Fellow
> Cornell University
>