Plot | MCMC.js

mcmc plot [target] renders MCMC diagnostic plots from a samples file. Like the diagnostics commands it is pure TypeScript, reads the same samples files and run refs, and shares --store, --stdin, --warmup, and --var.

mcmc plot --kind trace
mcmc plot --kind forest --format html -o forest.html

Plot kinds

Choose one with --kind (default forest). There are 19 kinds:

trace, density, histogram, rank, autocorr, pair, scatter, energy, forest, ecdf, cumulative-mean, running-rhat, violin, chain-intervals, chain-intervals-all, summary-table, diagnostics-heatmap, splom, parallel-coords.

A terminal forest plot looks like this:

parameter  mean & 94% HDI                         R-hat
alpha                       ────━●━━────         1.006   2.054  [1.601, 2.516]
beta                                        ─●─  1.003   2.991  [2.918, 3.064]
sigma     ─━●━─                                  1.002   0.344  [0.183, 0.528]

Output formats

--format chooses the renderer (default terminal):

terminal — Unicode braille and block glyphs printed to the terminal, with --ascii for a plain-ASCII fallback. --width and --height are in characters.
svg — standalone, publication-quality vector output. --width and --height are in pixels.
html — one self-contained, offline HTML page. Interactive charts (trace, density, and the like) embed uPlot inline for pan, zoom, and PNG/SVG export; forest, pair, and the table and grid kinds embed their SVG.

mcmc plot --kind trace --format svg -o trace.svg
mcmc plot --kind trace --format html -o trace.html

The HTML export is fully self-contained: open it in any browser with no network and no server. Nothing is fetched from a CDN.

Selecting variables and tuning

Flag	Meaning
`--var <name...>`	restrict to these variables (default: all)
`--hdi-prob <value>`	HDI credible mass for `forest` (default 0.94)
`--bins <n>`	histogram/rank bins (default: Freedman-Diaconis, or 20)
`--max-lag <n>`	autocorrelation max lag (default 40)
`--color-by <var>`	color scatter points by a third variable via viridis (svg/html)
`-o, --out <file>`	write the rendered plot to a file instead of stdout
`--json`	print the underlying plot data as JSON instead of rendering

--json is the data-builder output: the serializable object the renderers consume, useful if you want to render it yourself.

Interactive 3D in the browser

Three kinds, splom (scatter-plot matrix), parallel-coords, and a 3D point cloud, have interactive WebGL renderers in the separate @mcmcjs/plots-gl package, backed by regl. The CLI builds their data; mounting the interactive renderer into a live DOM element is a library call. See Plotting internals for the data-builder and renderer split.