Blog - chart domain calc

domainCalc.js

export function createDomain(values, symmetrical, includeZero) {
  const dMax = d3.max(values);
  const dMin = d3.min(values);
  if (symmetrical) {
    const largest = d3.max([Math.abs(dMax), Math.abs(dMin)]);
    return [-largest, largest];
  }
  if (includeZero) {
    if (dMin <= 0 && dMax <= 0) {
      return [dMin, 0];
    } else if (dMin >= 0 && dMax >= 0) {
      return [0, dMax];
    }
  }
  return [dMin, dMax];
}

/**
 * Extend domain by the given normalized amount
 */
export function extendDomain(domain, amt) {
  let l = ((domain[1] - domain[0]) * amt) || 1;
  return [domain[0] - l, domain[1] + l];
}