interpolated.js

export const interpolatedSteps = (geojson, numSteps = 4) => {
  let minMax = [];

  if (geojson.features.length < 1) {
    minMax = [1, numSteps];
  } else {
    minMax = geojson.features.reduce((minMax, feature) => {
      minMax[0] = Math.min(minMax[0] || feature.properties.hits, feature.properties.hits);
      minMax[1] = Math.max(minMax[1], feature.properties.hits);
      return minMax;
    }, [null, null]);

    if ((minMax[1] - minMax[0]) < (numSteps - 1)) {
      minMax[1] = minMax[0] + (numSteps - 1);
    }
  }

  const stepSize = (minMax[1] - minMax[0]) / (numSteps - 1);
  const steps = [minMax[0]];

  for (let i = 1; i <= numSteps - 1; i++) {
    steps.push(Math.round(minMax[0] + (stepSize * i)));
  }

  return steps;
}