Marey.Plot 0.3.0

Marey.Plot

The chart API of Marey, a dimensionally-typed visualization system for F#. This is the package most people install.

#r "nuget: Marey.Plot"
#r "nuget: Marey.Backend.Svg"

open Marey

let t = Array.init 24 (fun i -> float i * 0.4<s>)
let x = t |> Array.map (fun t -> 0.5 * 9.81<m/s^2> * t * t)

Chart.line U.second U.metre t x
|> Chart.withTitle "Free fall"
|> Chart.toSvg SvgBackend.render "fall.svg" (Chart.size 800.0 500.0)

That prints an x axis reading t [s] and a y axis reading x [m] with nothing configured. The scale, the domain, the SI prefix, the tick values, the tick labels and both axis titles are derived from the two unit witnesses. x is never annotated as a length — the compiler works that out — and plotting metres against metres on these axes is a compile error.

What is in it

• Chart — twelve geoms: line, scatter, area, bar, errorbar, step, ribbon, tile, rect, image, segment and text, with box plots and violins by category under Chart.Category. Most have an add* that layers onto the last panel, and Chart.Plain covers data that genuinely has no units.

• The plot encoding block — for data that is a table rather than two arrays. Declares x, y, colour, shape and size in one place, with each dimensioned channel checked against its witness.

• Channels. One colour or marker shape per category, with a legend that names the levels; or a colour or size driven by a quantity, which brings a colorbar labelled from its unit witness.

• Statistics — histogram, kernel density, ECDF, least-squares fit, and a five-number summary. The measures carry through: a fit of metres against seconds has a slope of type float<m/s>.

• Facets. facetWrap gives one panel per level of a key, over shared axes.

• Themes. Six, all measured against the colour validator below. Theme.tikz inherits the host LaTeX document's fonts.

• Palettes — Okabe–Ito, viridis, cividis, magma and an Oklab diverging ramp, with a colour-vision-deficiency and contrast validator that every shipped theme is checked against.

• A measure–arrange constraint layout, and the axis and legend compilers.

• The scene storyboard block, for a figure that moves:

  open Marey.Storyboard
  
  let intro =
      scene {
          let! curve = draw measured |> over 1.2<s>
          do! wait 0.5<s>
          do! parallel' [ curve |> morphTo fitted |> over 2.0<s>
                          curve |> zoomToX (0.0, 8.0) |> over 2.0<s> ]
          do! highlight curve.[42]
      }
  
  let anim = animate 32 (Chart.size 640.0 400.0) intro
  

  let! binds a name for something on stage; animate lays the whole shot out once, against the union of every state it sampled, so the panel holds still while the data moves. Seeking is evaluation, so anim.At 2.7<s> is a direct call and frames render in any order, in parallel.

• The frame writer. Film.ofStory pairs the scene animation with the layout it is drawn inside, and Frames.write renders every frame over Array.Parallel.map and numbers them onto disk as frame-00000.png. The concurrent and serial passes produce the same bytes in the same order, and one memoised ITextMeasurer serves the whole film — because font resolution walks a family stack against whatever is installed, and a measurer per thread is a chance for one frame of a video to be set in a different typeface from the frame before it.

• Per-layer styling that survives a theme change where it was set explicitly and is recoloured where it was not, which is what makes withTheme safe to apply last.

No backend reference

Marey.Plot does not depend on a renderer. A backend is a function passed in at render time, which is why the same figure goes to SVG or to LaTeX without the figure knowing either exists. Install one:

• Marey.Backend.Svg — pure F#, zero dependencies.
• Marey.Backend.Tikz — tikzpicture source for LaTeX, with siunitx units.

Depends on Marey.Core, Marey.Units and Marey.Anim — the last because the storyboard names an Anim and a Figure in one signature. It is 36 KB and has no dependencies of its own.

• The guide
• Examples