@data-ui/histogram/esm/utils/binNumericData.js

React + d3 library for creating histograms

import { histogram as d3Histogram, extent as d3Extent } from 'd3-array';
import { scaleLinear } from 'd3-scale';
var DEFAULT_BIN_COUNT = 10;
/*
 * handles binning of numeric data by series index
 * if binValues are passed, ignores other bin values that are encountered
 *
 * returns an object of bins keyed on series index with the following shape
 * {
 *   [seriesIdx]: Array<Object{
 *      bin0: String,
 *      bin1: String,
 *      data: Array<datum>,
 *      count: Number,
 *      id: String,
 *    }>,
 * }
 */

export default function binNumericData(_ref) {
  var allData = _ref.allData,
      _ref$binCount = _ref.binCount,
      userBinCount = _ref$binCount === void 0 ? DEFAULT_BIN_COUNT : _ref$binCount,
      binValues = _ref.binValues,
      limits = _ref.limits,
      rawDataByIndex = _ref.rawDataByIndex,
      valueAccessor = _ref.valueAccessor;
  var binCount = Array.isArray(binValues) ? binValues.length : userBinCount;
  var binsByIndex = {};
  var histogram = d3Histogram();
  var extent = d3Extent(allData, valueAccessor);

  if (binValues) {
    // account for extent of binValues if passed
    var binExtent = d3Extent(binValues);
    extent = [Math.min(binExtent[0], extent[0]), Math.max(binExtent[1], extent[1])];
  }

  var scale = scaleLinear().domain(extent).nice(binCount);
  histogram.domain(limits || scale.domain()).thresholds(binValues || scale.ticks(binCount));
  Object.keys(rawDataByIndex).forEach(function (index) {
    var data = rawDataByIndex[index];
    var seriesBins = histogram.value(valueAccessor)(data); // if the last bin equals the upper bound of the second to last bin, combine them
    // see https://github.com/d3/d3-array/issues/46#issuecomment-269873644

    var lastBinIndex = seriesBins.length - 1;
    var lastBin = seriesBins[lastBinIndex];
    var nextToLastBin = seriesBins[lastBinIndex - 1];
    var shouldCombineEndBins = nextToLastBin && nextToLastBin.x1 === lastBin.x0 && lastBin.x1 === lastBin.x0;
    var filteredBins = shouldCombineEndBins ? seriesBins.slice(0, -1) : seriesBins;
    binsByIndex[index] = filteredBins.map(function (bin, i) {
      return {
        bin0: bin.x0,
        // if the upper limit equals the lower one, use the delta between this bin and the last
        bin1: bin.x0 === bin.x1 ? i > 0 && bin.x0 + bin.x0 - seriesBins[i - 1].x0 || bin.x1 + 1 : bin.x1,
        data: [].concat(bin).concat(shouldCombineEndBins && (shouldCombineEndBins && i === lastBinIndex - 1 ? lastBin : [])),
        // if the last bin was inclusive / omitted, add its count to the last bin
        count: bin.length + (shouldCombineEndBins && i === lastBinIndex - 1 ? lastBin.length || 0 : 0),
        id: i.toString()
      };
    });
  });
  return binsByIndex;
}