function-plot/src/evaluate.ts at master · getwebtools/function-plot

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import globals from './globals'

import { interval, builtIn } from './samplers'

import { Chart } from './index'

import { FunctionPlotDatum } from './types'

const evalTypeFn = {

interval,

builtIn

}

/**

* Computes the endpoints x_lo, x_hi of the range

* from which the sampler will take samples

* @param {Object} scale

* @param {Object} d An item from `data`

* @returns {Array}

function computeEndpoints (scale: any, d: any): [number, number] {

const range = d.range || [-Infinity, Infinity]

const start = Math.max(scale.domain()[0], range[0])

const end = Math.min(scale.domain()[1], range[1])

return [start, end]

}

/**

* Decides which sampler function to call based on the options

* of `data`

* @param {Object} chart Chart instance which is orchestrating this sampling operation

* @param {Object} d a.k.a a single item from `data`

* @returns {Array}

function evaluate (chart: Chart, d: FunctionPlotDatum) {

const range = computeEndpoints(chart.meta.xScale, d)

const evalFn = evalTypeFn[d.sampler]

const nSamples = d.nSamples || Math.min(

globals.MAX_ITERATIONS,

globals.DEFAULT_ITERATIONS || (chart.meta.width * 2)

)

const data = evalFn(chart, d, range, nSamples)

// NOTE: it's impossible to listen for the first eval event

// as the event is already fired when a listener is attached

chart.emit('eval', data, d.index, d.isHelper)

return data

}

export default evaluate