math-interpolate

Install

$ yarn add math-interpolate

Interpolation cases usage

So, you can use methods below

• linear by ({ x, x1, y1, x2, y2 })
• bilinear by ({ x, y, x1, y1, x2, y2, q11, q12, q21, q22 })
• byInternalTable by ({ x, y, tableAsDoubleArray } TODO: external cases
• getKB for condition like y = (k * x) + b by { x1, y1, x2, y2 }
• getCommonPointByBisectionMethod by ({ fn1, fn2, xMin = -1000, xMax = 1000, eps = 0.001 })

linear

import { linear } from 'math-interpolate'

console.log(linear({ x: 0.5, x1: 0, y1: 1, x2: 1, y2: 2 }))
// 1.5

This example description

          |
y2= 2     |                           o
          |
y= ?      |             o
(1.5 will be found)
y1= 1     o
          |
          ------------------------------------
          x1= 0         x= 0.5        x2= 1

bilinear

import { bilinear } from 'math-interpolate'

console.log(
  bilinear({
    x1: 1,
    q11: 400,
    q12: 410,
    y1: 1,
    x2: 6,
    q21: 210,
    q22: 590,
    y2: 5,
    x: 3,
    y: 3.5,
  }),
)
// 377.75

This example description

          |   q12= 410                q22= 590
y2= 5     |   o                       o
          |
          |           q= ? (377.75 will be found)
y= 3.5    |           o
          |
          |   q11= 400                q21= 210
y1= 1     |   o                       o
          ------------------------------------
              x1= 1   x= 3            x2= 6

And also, you can read more about bilinear interpolation on wiki.

byInternalTable

Interpolate by table (only internal table values gives correct result) for example

import { byInternalTable } from 'math-interpolate'

const temperature = -21.0
const percentage = 20.0
/*
  About table below:
  1st horizontal line (highest row as x axis) - temperature conditions template
  1st vertical column (first left column as y axis) - percentage conditions template
*/
const tableAsDoubleArray = [
  [0.0, -30, -20.0, -10.0, 0.0, 20.0, 40.0, 60.0, 80.0, 100.0],
  [0.0, 4.19, 4.19, 4.19, 4.19, 4.19, 4.19, 4.19, 4.19, 4.19],
  [25.0, 3.93, 3.93, 3.93, 3.95, 3.98, 4.0, 4.03, 4.05, 4.08],
  [37.0, 3.68, 3.68, 3.7, 3.72, 3.77, 3.82, 3.88, 3.94, 4.0],
  [45.0, 3.49, 3.49, 3.52, 3.56, 3.62, 3.69, 3.76, 3.82, 3.89],
]

console.log(
  byInternalTable({
    x: temperature,
    y: percentage,
    tableAsDoubleArray,
  }),
)
// 3.982

getKB

import { getKB } from 'math-interpolate'

console.log(
  getKB({
    x1: 1,
    y1: 1,
    x2: 6,
    y2: 5,
  }),
)
// { k: -0.8,
//   b: 1.8 }

getCommonPointByBisectionMethod

import { getCommonPointByBisectionMethod } from 'math-interpolate'

console.log(
  getCommonPointByBisectionMethod({
    fn1: (x) => x,
    fn2: (x) => -x,
    xMin: -200, // -1000 by default
    xMax: 200, // 1000 by default
    eps: 0.001, // 0.001 by default (accuracy)
    iMax: 1000, // 1000 by default (max iterations number)
  }),
)
// { error: false,
//   x: ~0,
//   y: ~0 }

This example description

          |
y2= 2     o                           o
          |
y= ?      |             o
(~1.5 will be found)
y1= 1     o                           o
          |
          ------------------------------------
          x1= 0         x= ?          x2= 1
                        (~0.5 will be found)

import { getKB, getCommonPointByBisectionMethod } from 'math-interpolate'

const { k: k1, b: b1 } = getKB({ x1: 0, y1: 1, x2: 1, y2: 2 })
const { k: k2, b: b2 } = getKB({ x1: 0, y1: 2, x2: 1, y2: 1 })
const fn1 = (x) => k1 * x + b1
const fn2 = (x) => k2 * x + b2

console.log(
  getCommonPointByBisectionMethod({
    fn1,
    fn2,
  }),
)
// { error: false, // & description field if true
//   x: 0.5002021789550781,
//   y: 1.5002021789550781 }

Commands

• npm run clean - Remove lib/ directory
• npm test - Run tests with linting and coverage results.
• npm test:only - Run tests without linting or coverage.
• npm test:watch - You can even re-run tests on file changes!
• npm test:prod - Run tests with minified code.
• npm run test:examples - Test written examples on pure JS for better understanding module usage.
• npm run lint - Run ESlint with airbnb-config
• npm run cover - Get coverage report for your code.
• npm run build - Babel will transpile ES6 => ES5 and minify the code.
• npm run prepublish - Hook for npm. Do all the checks before publishing your module.

License

MIT © Den Pol