Curves

A curve is its own primitive, drawn over the rectangle of its board.

show << Plot::Add("sine", "fig", [](scalar x){ return std::sin(x); });

Sources

c++ Plot::Add(name, board, ...)

Plot::Add("f",   fig, [](scalar x){ return x*x; });   // a C++ callable
Plot::Add("res", fig, "residuals.csv");               // two columns
Plot::Add("pts", fig, points);                        // vector<vec2>
Plot::Add("y",   fig, ys, vec2(0, 10));               // values on a grid
Plot::FromSnippet("lua", fig, "profile");             // a Lua section

A callable and a Lua section are sampled over the board's x range (possibly time-dependent). A csv is re-read when it is saved, so a figure updates while the experiment runs.

What it publishes

Setting		Default
sine/color	the ink	next in the board's palette
sine/width	stroke width in pixels	3
sine/reveal	how much of it is drawn, 0 to 1	1

caption is what a legend calls the curve when its name is not what a reader wants.

Its shader

A curve's fragment program is written to views/<name>.glsl the first time it is shown, and drawn from there, see the board's page. It gets its samples as samples with the span they cover, plus color, line_width and reveal.

#include <plot.glsl> carries what a curve in data coordinates needs, see the shader stdlib. Example for a dashed curve:

#include <plot.glsl>
uniform sampler2D samples;
uniform vec2  span;
uniform vec4  color;
uniform float line_width, reveal;

void main() {
    vec2 px = iPixelXY(), p = iWorld();
    float d = sdGraph(p, dataAt(samples, span, p.x),
                         dataSlope(samples, span, p.x), px);
    float a = color.a * stroke(d, line_width)
            * dashMask(p, vec2(9.0, 6.0), px)      // mark, gap, in pixels
            * inSpan(p.x, span, px.x)
            * revealMask(p.x, span, reveal, px.x);
    fragColor = vec4(color.rgb, a);
}

Deck format

- plot: sine            # "board: fig" implied, the last board declared
  snippet: sine         # one source: snippet, data, values, points
  color: "#2f7fd1"
  width: 4
  caption: $\sin x$

A formula is a function snippet. data: is a csv of two columns, points: a list of [x, y], values: a list of numbers over an optional span: [min, max].