code: function combineRepeated(sortedValueArrays) {
    const result = new Array(sortedValueArrays.length);
    for (let i = 0; i < result.length; i++) {
      result[i] = [sortedValueArrays[i][0]];
    }
    for (let j = 1; j < sortedValueArrays[0].length; j++) {
      if (sortedValueArrays[0][j] === sortedValueArrays[0][j - 1]) {
        const currentIndex = result[0].length - 1;
        for (let i = 0; i < result.length; i++) {
          if (result[i][currentIndex] === undefined) {
            result[i][currentIndex] = sortedValueArrays[i][j];
          }
        }
      } else {
        for (let i = 0; i < result.length; i++) {
          result[i].push(sortedValueArrays[i][j]);
        }
      }
    }
    return result;
  }
docs: @param  {Array[]} sortedJulianDateOrValueArrays The array of arrays of values to combine. These must be sortedByFirst. Dates must be JulianDates.
  @param  {Integer} [firstColumnType] Eg. VarType.TIME.
  @return {Array[]} The values, with any repeats in the first column combined into one. Dates are converted to ISO8601 string representation.
  
  Eg.
  var x = [['a', 'b', 'b', 'c'], [1, 2, undefined, 3], [4, undefined, 5, undefined]];
  combineRepeated(x);
  # x is [['a', 'b', 'c'], [1, 2, 3], [4, 5, undefined]].