log.md

Log

Similar to linear scales, except an logarithmic transform is applied to the input domain value before the output range value is computed. Each range value y can be expressed as a function of the domain value x: y = log(x) + b. (online demo)

Usage

import { Log, LogOptions } from '@antv/scale';

const options: LogOptions = {
  domain: [1, 10],
  range: [0, 1],
  base: 10
};

const x = new Log(options);

x.map(1); // 0
x.map(2); // 0.301
x.invert(0.301); // 2

More usages reference linear scale.

Options

Key	Description	Type	Default
domain	Sets the scale’s domain to the specified array of values. A log scale domain must be strictly-positive or strictly-negative; the domain must not include or cross zero.	number[]	[0, 1]
range	Sets the scale’s range to the specified array of values.	<code>number[] &#124; string[]</code>	[0, 1]
unknown	Sets the output value of the scale for undefined (or NaN) input values.	any	undefined
tickCount	Sets approximately count representative values from the scale’s domain. The specified tickCount in options is only a hint: the scale may return more or fewer values depending on the domain.	number	5
tickMethod	Sets the method for computing representative values from the scale’s domain.	(min: number, max: number, count: number, base: number) => number[]	d3-ticks
round	Rounds the output of map or invert if it is true.	boolean	false
clamp	Constrains the return value of map within the scale’s range if it is true.	boolean	false
nice	Extends the domain so that it starts and ends on nice round values if it is true.	boolean	false
interpolate	Sets the scale’s range interpolator factory if it is specified.	(a: number, b: number) => (t: number) => number	(a, b) => (t) => a * (1 - t) + b * t
base	Sets the base for this logarithmic scale if it is specified.	number	10

Methods

# map(x: number): number

Given a value in the input domain, returns the corresponding value in the output range if it is not undefined (or NaN), otherwise options.unknown

# invert(x: number): number

Given a value from the range, returns the corresponding value from the domain.

# update(options: LogOptions): void

Updates the scale's options and rescale.

# getOptions(): LogOptions

Returns the scale's current options.

# clone(): Log

Returns a new Log scale with the independent and same options as the original one.

# getTicks(): number[]

Returns representative values from the scale’s domain computed by specified options.tickMethod with options.tickCount.