Charming Scale

Charming Scale maps abstract values to visual values. Scales are used by transforms and can be called directly. A scale is a function, so any function that maps a value works where a scale is expected, including d3-scale scales.

const x = cm.scaleLinear([0, 10], [0, 100]);
x(5); // 50

cm.scaleLinear(domain[, range[, options]])

Returns a linear scale that maps the continuous domain to the continuous range (default [0, 1]). Values outside the domain are extrapolated. Options:

• unknown — the output for null and NaN inputs (default undefined).
• interpolate — a function that maps a normalized value between 0 and 1 to an output, used instead of the range.

const scale = cm.scaleLinear([0, 1], [0, 100]);
scale(0); // 0
scale(0.5); // 50
scale(1); // 100

cm.scaleSqrt(domain[, range[, options]])

Like cm.scaleLinear, but applies a square root to the input first.

const scale = cm.scaleSqrt([0, 1], [0, 100]);
scale(0.09); // 30
scale(0.64); // 80
scale(0.81); // 90

cm.scaleLog(domain[, range[, options]])

Like cm.scaleLinear, but applies a logarithm to the input first.

const scale = cm.scaleLog([1, 10], [0, 1]);
scale(Math.sqrt(10)); // 0.5

cm.scaleOrdinal(domain, range[, options])

Returns an ordinal scale that maps each value of the discrete domain to the value of range at the same index. The range repeats if it's shorter than the domain. Options:

• unknown — the output for values not in the domain (default undefined).

const scale = cm.scaleOrdinal(["A", "B", "C"], ["steelblue", "yellow", "red"]);
scale("A"); // "steelblue"
scale("B"); // "yellow"
scale("C"); // "red"