LogarScale

This lightweight npm package can be used to calculate a simple logarithmic scale between two given values (minimum and maximum) and the base.

It handles negative values as well as any positiv logarithmic base.

This package is no longer actively developed, maintained or supported.
Please use the scalax package instead.

Install

Using Node.js, install the package with the following shell command:

npm install logarscale

Usage

Load the package into your project:

const LogarScale = require( 'logarscale' );

Sample of how to use the package in your code:

let scale = new LogarScale( -1.341, 6.5, 2 );

if ( scale.calculate() ) {

    let min = scale.getMinimum();
    // expected: -2

    let max = scale.getMaximum();
    // expected: 8

    let ticks = scale.getTicks( false );
    // expected: [ -2, 0, 2, 4, 8 ]

    let pct = scale.pct( 2 );
    // expected: 50

    let crossesZero = scale.crossesZero();
    // expected: true

}

JavaScript

Using JavaScript load this package by embed this file via jsDelivr:

import LogarScale from 'https://cdn.jsdelivr.net/npm/logarscale@1.0.0/+esm';

Remember: To use import you need to load your JavaScript file as type="module".

API

Here you can find all methods available in the LogarScale class.

Creating a new instance of LogarScale allows to pass the bounds and logarithmic base. This replaces methods setBounds and setBase. You still need to run calculate().

setBounds( min, max )

Set lower / upper bounds for the scale. Requires to run calculate() afterwards.

setBase( base )

Set logarithmic scale for the scale. Can be any positiv number. Requires to run calculate() afterwards.

centerAt ( [ value = 0 ] )

Center scale at the given value (default is zero). Requires to run calculate() afterwards.

calculate()

Calculates the scale range, minimum, maximum and multiple other things.

isNegative()

Checks if the entire scale is negative. Returns true if the scale is negative.

crossesZero()

Checks if the scale crosses zero. Returns true if the scale crosses zero.

getRange()

Returns the scale range (from min to max).

getMinimum()

Returns the scale minium value.

getMaximum()

Returns the scale maximum value.

getTicks( [ pow0 = true ] )

Returns an array of the scale ticks (ascending order).

If pow0 = false, ticks for x^0 on both sides the scale (negative and positive) will be excluded. This only hits when the scale has positive and negative values (crosses zero).

getTicksReverse( [ pow0 = true ] )

Returns an array of the scale ticks (descending order).

pct( value [, from = 'min' ] )

Returns the percentage of a value within the scale from the reference point (either minimum or maximum value).

Patch notes

1.0.1

• Successor scalax takes over this package

1.0.0

• Initial release