YTEP-0021: Particle-Only Plots¶
Created: August 29, 2014 Author: Andrew Myers
This YTEP describes a mechanism for creating scatter plots of particle fields in yt. It was prompted by a question posted to the yt-users list by Jeremy Ritter, linked below.
Essentially, it proposes creating a user-facing function called
ParticlePlot (analagous to
ProfilePlot) that facilitates plotting arbitrary
particle fields against one another.
Currently, to make plots like those in the linked notebooks, you would have to grab the particle data from the data source and feed them to something like pyplot.plot().
Instead of units, labels, and log_scales getting grabbed from the
FieldInfoContainer, they would need to be set up manually. Furthermore, the standardized interface for modifying
yt plots that exists in
PlotWindow would not be available.
Instead, we could create a
ParticlePlot class that would act like the currently existing yt plotting classes. The constructor would take:
x_fields: str or list, the field(s) to put on the x-axis
y_fields: str or list, same but for the y-axis
color: either a color string, or another particle field to be mapped to a color scale
If x_fields and y_fields are strings, this would add a single scatter plot to the
ParticlePlot. If they are lists of field_names, then a series of plots will be added, in the
style of (for example)
PhasePlot. The standard methods for modifying these plots (e.g.
set_cmap, etc. ) should all work as expected, and they
should be able to be saved / sent to the notebook as normal.
My current implementation wraps pyplot.plot(), but because pyplot.plot can be slow when the number of points is large,
ParticlePlot should instead use Sam Skillman’s particle
splatting code to create something like a
FixedResolutionBuffer. This could then be displayed with pyplot.imshow(). This would also make it easy for users to access the raw image
and pass it to another plotting routine, if they prefer.
ParticlePlot shares a lot of its functionality with
PhasePlot, so the implementation should be similar. In particular,
ParticlePlot should inherit from
and the individual plots in it should be
ParticlePlotMPL objects that inherit from
Plots that have spatial variables on both axes are logically different from those that don’t in a few ways. For instance, it could be misleading if the aspect ratios are
different for two spatial axes, as in the second linked notebook. Also, things like “pan” and “zoom” make sense for spatial data, but not when plotting, say, velocity
versus position. Should we handle spatial plots differently, as Nathan suggested in the yt-dev discussion above? Spatial plots could in inherit from
take advantage of all the methods and callbacks in there.
None; all existing code should work exactly as before.
Alternatively, there could be no mechanism for making particle scatter plots inside of yt, and users could call pyplot.plot() or whatever directly.