pcolormesh

Render a 2D scalar field as a pseudocolor mesh. This is the standard way to draw a density/heatmap in Jarvis-PLOT, and the recommended renderer for the output of the posterior_density and profile transforms.

Matplotlib: Axes.pcolormesh. Jarvis-PLOT wraps it: it accepts both an already-gridded field and scattered (x, y, z) points, which it bins onto a regular mesh for you.

Axes: rectangular (ax) and ternary (axtri).

Coordinates

Key	Required	Meaning
x	yes	Cell x positions
y	yes	Cell y positions
z	yes	Scalar value per cell (mapped through cmap)

If x/y/z come from a density/profile transform they are already gridded. If they are scattered points, Jarvis-PLOT bins them using the bin/objective/limit options below.

Style

Key	Type	Purpose
cmap	string	Colormap
vmin / vmax	float	Color scale limits
norm	string	Color normalization (e.g. log)
alpha	0–1	Opacity
edgecolor	color	Cell edge color (default none)
zorder	number	Draw order

Gridding controls (used only when the input is scattered):

Key	Default	Purpose
bin	from axes	Number of bins per side of the regular mesh
objective	max	How to reduce multiple points in a cell: max, min, mean
xlim / ylim	axis limits	Mesh extent
xscale / yscale	axis scale	linear or log binning

Example — render a posterior density

- name: density
  data:
    - source: df
      transform:
        - posterior_density:
            x: {expr: xx, lim: [0, 5]}
            y: {expr: yy, lim: [0, 5]}
            weight: {expr: "exp(LogL)"}
            bins: 120
            grid: 300
  axes: ax
  method: pcolormesh
  coordinates:
    x: {expr: x}
    y: {expr: y}
    z: {expr: density}
  style:
    cmap: jarvis_rainbow2_r
    vmin: 0
    vmax: 0.8
    edgecolor: none
  colorbar: axc

Notes

• Set the layer's colorbar (e.g. axc) and use a *cmap style card to show a colorbar.
• pcolormesh is faster and usually preferable to pcolor.
• To interpolate scattered points to a smooth field instead of binning, use the make_interp_2d transform first, or the jpfield method.

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See also: Plot Methods index · jpfield · contourf · voronoi