[yt-dev] Particle phase plotting

[Andrew Myers]

Hi John,

When I originally did this, I needed CIC deposition in phase space for a
project I was working on, so that was the use case I had in mind. I'm
wasn't sure that it made sense to use logarithmically-spaced bins for
finite-sized particles, so I just disabled log bins for particle phase
plots.

But, the default interpolation option is nearest grid point, which should
be equivalent to binning. I don't think there's any reason why NGP can't
work with log bins. It think the thing to do is soften the check to only
disable logging bin_fields when deposition='cic'.

-Andrew

On Fri, May 6, 2016 at 8:39 AM, John Zuhone <jzuhone at gmail.com> wrote:

> Hi all,
>
> I had a question about how we do particle phase plots / 2d profiles.
>
> I’ve noticed that we way we do this involves some kind of deposition of
> the particle data into a grid. This necessitates never allowing one to make
> log-spaced bins for a particle 2d profile, though you can of course plot
> them in logspace.
>
> This has rather nasty consequences, however, for data which has a huge
> dynamic range over orders of magnitude and for which log-spaced bins would
> make a lot of sense. See, for example, this plot:
>
> http://i.imgur.com/RvCp3uD.png
>
> where a lot of the interesting data is at low density but has simply been
> swallowed up into the first bin in density space because of the linear
> spacing, making the plot essentially useless. Note this plot was made with
> a ridiculous amount of bins, 16000x16000, and it still washes things out at
> low density too much.
>
> So I guess my questions are:
>
> 1. Why do we need to use deposition instead of simply binning up the
> particle data? Isn’t this what we do for grid-spaced data?
>
> 2. Is there any reason why we cannot use log-spaced bins with deposition
> (even if we have to hack it somehow)?
>
> Best,
>
> John
>
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