Charts

Package: CHART_PACKAGE. Registered by createEngine(); for a slimmer engine, register it explicitly (see choosing packages).

The engine never draws. A chart result is a specification, the points to draw, the axes’ extents, and a plain-text label, that your application hands to its own charting library. The examples below are real results; the notepad on this page draws them with a deliberately tiny built-in renderer, purely so the docs can demo the shape. In your own app, you bring the charting library.

Both forms below produce one value type, Chart, with a kind that says how to render it, so a host writes one switch and gets every chart the engine can produce, today and later.

Sparklines

<vector> as sparkline turns a numeric vector or a range into a sparkline: the same numbers, drawn as a shape.

[120, 135, 128, 150, 162] as sparkline // [120, 135, 128, 150, 162]
map(x^2, 0:5) as sparkline // [0, 1, 4, 9, 16, 25]

Only a purely numeric vector (a single row or column) or a range can become a sparkline; anything else is a clear error rather than an empty chart. The text answer keeps the numbers, so a reader with no canvas still sees them. The series is downsampled to at most 32 points, so a wide range costs nothing to draw.

Function plots

plot <expr> from <a> to <b> samples an expression across a range and draws its curve.

plot x^2 from -3 to 3 // x^2 over [-3, 3]
plot sin(x) from 0 to 2pi // sin(x) over [0, 6.28]
plot 1000 * 1.05^x from 0 to 10 // 1000 * 1.05^x over [0, 10]
plot 1/x from 0.5 to 5 // 1/x over [0.5, 5]

The variable is x, the same reserved name map(x^2, 0:5) binds, and the expression is re-evaluated at each of 64 steps across the range, so the sample is exact rather than interpolated. A step the expression cannot evaluate, 1/x at zero, is left as a gap in the curve rather than breaking the whole plot. plot stays an ordinary word elsewhere, so plot remains usable as a variable name; only plot followed by an expression begins a plot.

The data, not the picture

A Chart value carries everything a renderer needs and nothing it does not: the kind (sparkline or plot), the (x, y) points, the domain and range they are scaled to, the source expr for a plot, and the label you have seen in the answers above. It never carries pixels. This is the same split the colour swatch and the matrix grid already use: the engine produces the numbers, the host draws them. The chart package is on by default and removable, so an engine that wants no charting drops it and these two forms simply stop parsing.