code: function getFractionalValue(legendHelper, value) {
    var extremes = getExtremes(
      legendHelper.tableColumn,
      legendHelper.tableColumnStyle
    );
    var f =
      extremes.maximum === extremes.minimum
        ? 0
        : (value - extremes.minimum) / (extremes.maximum - extremes.minimum);
    if (legendHelper.tableColumnStyle.clampDisplayValue) {
      f = Math.max(0.0, Math.min(1.0, f));
    }
    return f;
  }
docs: Convert a value to a fractional value, eg. in a column that ranges from 0 to 100, 20 -> 0.2.
  TableStyle can override the minimum and maximum of the range.
  @private
  @param  {Number} value The value.
  @return {Number} The fractional value.