Package Exports

linear-converter

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Readme

linear-converter

Flexible linear converter with built in conversions for common units

Install

npm i linear-converter

Basic usage

var lc = require('linear-converter');

lc.convert(25, lc.PRESETS.temperature.celsiusToFahrenheit); // => 77

Preset inversion

The provided presets go in one direction only; to invert the direction, use invertPreset:

lc.convert(77, lc.invertPreset(lc.PRESETS.temperature.celsiusToFahrenheit)); // => 25

Presets composition

The provided presets have a base unit from which to convert. Any to any conversions are straightforward using inversion and composition with composePresets:

var kelvinToFahrenheit = lc.composePresets([
  lc.invertPreset(lc.PRESETS.temperature.celsiusToKelvin),
  lc.PRESETS.temperature.celsiusToFahrenheit
]);

lc.convert(293.15, kelvinToFahrenheit); // => 68

Custom conversions

Custom conversions are easily achieved by passing an array with 2 scales, each of those an array with 2 values. For example, [[0, 1], [0, 2]] means that 0 and 1 in the first scale map to 0 and 2 in the second scale respectively; in short, it multiplies by 2. Any linear function can be described that way:

// f(x) = ax + b
lc.convert(x, [[0, 1], [b, a+b]]); // => ax + b
lc.convert(x, [[1/a, -b/a], [b+1, 0]]); // => ax + b

For an arbitrary f(x) = ax + b, any [[x₁, x₂], [f(x₁), f(x₂)]] is a valid preset.

More examples:

// degrees to radians
lc.convert(240, [[0, 180], [0, Math.PI]]); // => 4 * Math.PI / 3

// f(x) = 3x
lc.convert(5, [[0, 1/3], [0, 1]]); // => 15

// f(x) = -2x - 46
lc.convert(-23, [[0, 1], [-46, -48]]); // => 0

Coefficients

Creating presets from a given function is trivial; to find the function from a given preset, two methods are provided: getCoefficientA and getCoefficientB.

// f(x) = 2x + 1
lc.getCoefficientA([[0, 1], [1, 3]]); // => 2
lc.getCoefficientB([[0, 1], [1, 3]]); // => 1

// f(x) = ax + b
lc.getCoefficientA([[x1, x2], [f(x1), f(x2)]]); // => a
lc.getCoefficientB([[x1, x2], [f(x1), f(x2)]]); // => b

See more

rescale: rescales a point given two scales.
scale: scales normalised data.
normalise: normalise data to [0, 1].
rescale-util: rescale utilities.