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  • License MIT

Flexible linear converter

Package Exports

  • linear-converter

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (linear-converter) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

linear-converter

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Flexible linear converter

Table of contents

Installation

npm

npm i linear-converter

Bower

bower install linear-converter

To use it in the browser, include the following on your site:

<script src="bower_components/linear-converter/dist/linear-converter.min.js"></script>

Basic usage

linear-converter uses arbitrary-precision to support arbitrary precision. See all available adapters.

var Decimal = require('arbitrary-precision')(require('floating-adapter'));
var lc = require('linear-converter')(Decimal);

var temp = require('linear-presets').PRESETS.temperature;

lc.convert(temp.celsiusToFahrenheit, 25); // => new Decimal('77')

// also accepts Decimals
lc.convert(temp.celsiusToFahrenheit, new Decimal('25'));

For a quick interactive intro, see CodePen example.

Variants:

Preset inversion

var fahrenheitToCelsius = lc.invertPreset(temp.celsiusToFahrenheit);

lc.convert(fahrenheitToCelsius, 77); // => 25 (as decimal)

Presets composition

var kelvinToFahrenheit = lc.composePresets(
  lc.invertPreset(temp.celsiusToKelvin),
  temp.celsiusToFahrenheit
);

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

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 conversion can be described that way:

// f(x) = ax + b
lc.convert([[0, 1], [b, a+b]], x); // => ax + b
lc.convert([[1/a, -b/a], [b+1, 0]], x); // => 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([[0, 180], [0, Math.PI]], 240); // => 4 * Math.PI / 3

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

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

Preset equivalence

// f(x) = -3x + 6
lc.equivalentPresets(
  [[1, 5], [3, -9]],
  [[-1, 100], [9, -294]]
); // => true

lc.equivalentPresets(
  [[0, 1], [0, 2]], // f(x) = 2x
  [[0, 1], [0, 3]]  // f(x) = 3x
); // => false

Arbitrary precision

Arbitrary precision support is provided via arbitrary-precision. See all available adapters.

// without arbitrary precision (very lightweight)
var Decimal = require('arbitrary-precision')(require('floating-adapter'));
var lc = require('linear-converter')(Decimal);

lc.getCoefficientA([[0, 0.1], [0.1, 0.3]]); // => 1.9999999999999998

// with arbitrary precision
var Decimal = require('arbitrary-precision')(require('bigjs-adapter'));
var lc = require('linear-converter')(Decimal);

lc.getCoefficientA([[0, 0.1], [0.1, 0.3]]); // => 2

See CodePen example.

Currying

The convert function is designed to play nicely with currying:

var curry = require('lodash.curry');

var curriedConvert = curry(lc.convert);

var celsiusToFahrenheit = curriedConvert(temp.celsiusToFahrenheit);
var fahrenheitToCelsius = curriedConvert(lc.invertPreset(temp.celsiusToFahrenheit));

celsiusToFahrenheit(25); // => new Decimal('77')
fahrenheitToCelsius(77); // => new Decimal('25')

See CodePen example.

See more