crossfilter/src/bisect.js

Fast multidimensional filtering for coordinated views.

var bisect = crossfilter.bisect = bisect_by(crossfilter_identity);

bisect.by = bisect_by;

function bisect_by(f) {

  // Locate the insertion point for x in a to maintain sorted order. The
  // arguments lo and hi may be used to specify a subset of the array which
  // should be considered; by default the entire array is used. If x is already
  // present in a, the insertion point will be before (to the left of) any
  // existing entries. The return value is suitable for use as the first
  // argument to `array.splice` assuming that a is already sorted.
  //
  // The returned insertion point i partitions the array a into two halves so
  // that all v < x for v in a[lo:i] for the left side and all v >= x for v in
  // a[i:hi] for the right side.
  function bisectLeft(a, x, lo, hi) {
    while (lo < hi) {
      var mid = lo + hi >>> 1;
      if (f(a[mid]) < x) lo = mid + 1;
      else hi = mid;
    }
    return lo;
  }

  // Similar to bisectLeft, but returns an insertion point which comes after (to
  // the right of) any existing entries of x in a.
  //
  // The returned insertion point i partitions the array into two halves so that
  // all v <= x for v in a[lo:i] for the left side and all v > x for v in
  // a[i:hi] for the right side.
  function bisectRight(a, x, lo, hi) {
    while (lo < hi) {
      var mid = lo + hi >>> 1;
      if (x < f(a[mid])) hi = mid;
      else lo = mid + 1;
    }
    return lo;
  }

  bisectRight.right = bisectRight;
  bisectRight.left = bisectLeft;
  return bisectRight;
}