feat(scales): add reverse option to symlog scale

packages/scales/index.d.ts

@@ -54,6 +54,7 @@ declare module '@nivo/scales' {
         constant?: number
         min?: 'auto' | number
         max?: 'auto' | number
+        reverse?: boolean
     }
 
     export interface BandScale {

packages/scales/src/symlogScale.js

@@ -10,7 +10,7 @@ import { scaleSymlog } from 'd3-scale'
 import PropTypes from 'prop-types'
 
 export const symlogScale = (
-    { axis, constant = 1, min = 'auto', max = 'auto' },
+    { axis, constant = 1, min = 'auto', max = 'auto', reverse = false },
     xy,
     width,
     height
@@ -29,11 +29,13 @@ export const symlogScale = (
     }
 
     const scale = scaleSymlog()
-        .domain([minValue, maxValue])
         .constant(constant)
         .rangeRound(axis === 'x' ? [0, size] : [size, 0])
         .nice()
 
+    if (reverse === true) scale.domain([maxValue, minValue])
+    else scale.domain([minValue, maxValue])
+
     scale.type = 'symlog'
 
     return scale
@@ -44,4 +46,5 @@ export const symLogScalePropTypes = {
     constant: PropTypes.number,
     min: PropTypes.oneOfType([PropTypes.oneOf(['auto']), PropTypes.number]),
     max: PropTypes.oneOfType([PropTypes.oneOf(['auto']), PropTypes.number]),
+    reverse: PropTypes.bool,
 }

packages/scales/tests/symlogScale.test.js

@@ -0,0 +1,69 @@
+import { symlogScale } from '../src/symlogScale'
+
+it(`should be able to build a symlog scale for x axis`, () => {
+    const scale = symlogScale({ axis: 'x' }, { x: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale(0)).toBe(0)
+    expect(scale(0.5)).toBe(58)
+    expect(scale(1)).toBe(100)
+})
+
+it(`should be able to build a symlog scale for y axis`, () => {
+    const scale = symlogScale({ axis: 'y' }, { y: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale(0)).toBe(100)
+    expect(scale(0.5)).toBe(42)
+    expect(scale(1)).toBe(0)
+})
+
+it(`should allow to define min value for x axis`, () => {
+    const scale = symlogScale({ axis: 'x', min: 0.5 }, { x: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale.domain()[0]).toBe(0.5)
+    expect(scale(0)).toBe(-141)
+    expect(scale(0.5)).toBe(0)
+    expect(scale(1)).toBe(100)
+})
+
+it(`should allow to define min value for y axis`, () => {
+    const scale = symlogScale({ axis: 'y', min: 0.5 }, { y: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale.domain()[0]).toBe(0.5)
+    expect(scale(0)).toBe(241)
+    expect(scale(0.5)).toBe(100)
+    expect(scale(1)).toBe(0)
+})
+
+it(`should allow to define max value for x axis`, () => {
+    const scale = symlogScale({ axis: 'x', max: 2 }, { x: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale.domain()[1]).toBe(2)
+    expect(scale(0)).toBe(0)
+    expect(scale(0.5)).toBe(37)
+    expect(scale(1)).toBe(63)
+})
+
+it(`should allow to define max value for y axis`, () => {
+    const scale = symlogScale({ axis: 'y', max: 2 }, { y: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale.domain()[1]).toBe(2)
+    expect(scale(0)).toBe(100)
+    expect(scale(0.5)).toBe(63)
+    expect(scale(1)).toBe(37)
+})
+
+it(`should allow to reverse domain`, () => {
+    const scale = symlogScale({ axis: 'y', reverse: true }, { y: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale(0)).toBe(0)
+    expect(scale(0.5)).toBe(58)
+    expect(scale(1)).toBe(100)
+})
+
+it(`should allow to adjust the constant`, () => {
+    const scale = symlogScale({ axis: 'x', constant: 0.1 }, { x: { min: 0, max: 1 } }, 100, 100)
+
+    expect(scale(0)).toBe(0)
+    expect(scale(0.5)).toBe(75)
+    expect(scale(1)).toBe(100)
+})