charts/src/js/utils/intervals.js

import { floatTwo } from "./helpers";

function normalize(x) {
  // Calculates mantissa and exponent of a number
  // Returns normalized number and exponent
  // https://stackoverflow.com/q/9383593/6495043

  if (x === 0) {
    return [0, 0];
  }
  if (isNaN(x)) {
    return { mantissa: -6755399441055744, exponent: 972 };
  }
  var sig = x > 0 ? 1 : -1;
  if (!isFinite(x)) {
    return { mantissa: sig * 4503599627370496, exponent: 972 };
  }

  x = Math.abs(x);
  var exp = Math.floor(Math.log10(x));
  var man = x / Math.pow(10, exp);

  return [sig * man, exp];
}

function getChartRangeIntervals(max, min = 0) {
  let upperBound = Math.ceil(max);
  let lowerBound = Math.floor(min);
  let range = upperBound - lowerBound;

  let noOfParts = range;
  let partSize = 1;

  // To avoid too many partitions
  if (range > 5) {
    if (range % 2 !== 0) {
      upperBound++;
      // Recalc range
      range = upperBound - lowerBound;
    }
    noOfParts = range / 2;
    partSize = 2;
  }

  // Special case: 1 and 2
  if (range <= 2) {
    noOfParts = 4;
    partSize = range / noOfParts;
  }

  // Special case: 0
  if (range === 0) {
    noOfParts = 5;
    partSize = 1;
  }

  let intervals = [];
  for (var i = 0; i <= noOfParts; i++) {
    intervals.push(lowerBound + partSize * i);
  }
  return intervals;
}

function getChartIntervals(maxValue, minValue = 0) {
  let [normalMaxValue, exponent] = normalize(maxValue);
  let normalMinValue = minValue ? minValue / Math.pow(10, exponent) : 0;

  // Allow only 7 significant digits
  normalMaxValue = normalMaxValue.toFixed(6);

  let intervals = getChartRangeIntervals(normalMaxValue, normalMinValue);
  intervals = intervals.map((value) => {
    // For negative exponents we want to divide by 10^-exponent to avoid
    // floating point arithmetic bugs. For instance, in javascript
    // 6 * 10^-1 == 0.6000000000000001, we instead want 6 / 10^1 == 0.6
    if (exponent < 0) {
      return value / Math.pow(10, -exponent);
    }
    return value * Math.pow(10, exponent);
  });
  return intervals;
}

export function calcChartIntervals(values, withMinimum = false) {
  //*** Where the magic happens ***

  // Calculates best-fit y intervals from given values
  // and returns the interval array

  let maxValue = Math.max(...values);
  let minValue = Math.min(...values);

  // Exponent to be used for pretty print
  let exponent = 0,
    intervals = []; // eslint-disable-line no-unused-vars

  function getPositiveFirstIntervals(maxValue, absMinValue) {
    let intervals = getChartIntervals(maxValue);

    let intervalSize = intervals[1] - intervals[0];

    // Then unshift the negative values
    let value = 0;
    for (var i = 1; value < absMinValue; i++) {
      value += intervalSize;
      intervals.unshift(-1 * value);
    }
    return intervals;
  }

  // CASE I: Both non-negative

  if (maxValue >= 0 && minValue >= 0) {
    exponent = normalize(maxValue)[1];
    if (!withMinimum) {
      intervals = getChartIntervals(maxValue);
    } else {
      intervals = getChartIntervals(maxValue, minValue);
    }
  }

  // CASE II: Only minValue negative
  else if (maxValue > 0 && minValue < 0) {
    // `withMinimum` irrelevant in this case,
    // We'll be handling both sides of zero separately
    // (both starting from zero)
    // Because ceil() and floor() behave differently
    // in those two regions

    let absMinValue = Math.abs(minValue);

    if (maxValue >= absMinValue) {
      exponent = normalize(maxValue)[1];
      intervals = getPositiveFirstIntervals(maxValue, absMinValue);
    } else {
      // Mirror: maxValue => absMinValue, then change sign
      exponent = normalize(absMinValue)[1];
      let posIntervals = getPositiveFirstIntervals(absMinValue, maxValue);
      intervals = posIntervals.reverse().map((d) => d * -1);
    }
  }

  // CASE III: Both non-positive
  else if (maxValue <= 0 && minValue <= 0) {
    // Mirrored Case I:
    // Work with positives, then reverse the sign and array

    let pseudoMaxValue = Math.abs(minValue);
    let pseudoMinValue = Math.abs(maxValue);

    exponent = normalize(pseudoMaxValue)[1];
    if (!withMinimum) {
      intervals = getChartIntervals(pseudoMaxValue);
    } else {
      intervals = getChartIntervals(pseudoMaxValue, pseudoMinValue);
    }

    intervals = intervals.reverse().map((d) => d * -1);
  }

  return intervals.sort((a, b) => a - b);
}

export function getZeroIndex(yPts) {
  let zeroIndex;
  let interval = getIntervalSize(yPts);
  if (yPts.indexOf(0) >= 0) {
    // the range has a given zero
    // zero-line on the chart
    zeroIndex = yPts.indexOf(0);
  } else if (yPts[0] > 0) {
    // Minimum value is positive
    // zero-line is off the chart: below
    let min = yPts[0];
    zeroIndex = (-1 * min) / interval;
  } else {
    // Maximum value is negative
    // zero-line is off the chart: above
    let max = yPts[yPts.length - 1];
    zeroIndex = (-1 * max) / interval + (yPts.length - 1);
  }
  return zeroIndex;
}

export function getRealIntervals(max, noOfIntervals, min = 0, asc = 1) {
  let range = max - min;
  let part = (range * 1.0) / noOfIntervals;
  let intervals = [];

  for (var i = 0; i <= noOfIntervals; i++) {
    intervals.push(min + part * i);
  }

  return asc ? intervals : intervals.reverse();
}

export function getIntervalSize(orderedArray) {
  return orderedArray[1] - orderedArray[0];
}

export function getValueRange(orderedArray) {
  return orderedArray[orderedArray.length - 1] - orderedArray[0];
}

export function scale(val, yAxis) {
  return floatTwo(yAxis.zeroLine - val * yAxis.scaleMultiplier);
}

export function isInRange(val, min, max) {
  return val > min && val < max;
}

export function isInRange2D(coord, minCoord, maxCoord) {
  return (
    isInRange(coord[0], minCoord[0], maxCoord[0]) &&
    isInRange(coord[1], minCoord[1], maxCoord[1])
  );
}

export function getClosestInArray(goal, arr, index = false) {
  let closest = arr.reduce(function (prev, curr) {
    return Math.abs(curr - goal) < Math.abs(prev - goal) ? curr : prev;
  }, []);

  return index ? arr.indexOf(closest) : closest;
}

export function calcDistribution(values, distributionSize) {
  // Assume non-negative values,
  // implying distribution minimum at zero

  let dataMaxValue = Math.max(...values);

  let distributionStep = 1 / (distributionSize - 1);
  let distribution = [];

  for (var i = 0; i < distributionSize; i++) {
    let checkpoint = dataMaxValue * (distributionStep * i);
    distribution.push(checkpoint);
  }

  return distribution;
}

export function getMaxCheckpoint(value, distribution) {
  return distribution.filter((d) => d < value).length;
}