code: function findLargestInCol (M, i, startAtRow = 0) {
    let me = M.elements;
    let n = M.dimension;
    let offset = i * n;
    let maxIdx = startAtRow;
    let maxVal = _Math.abs(me[offset + maxIdx]);
    for (let i = maxIdx + 1; i < n; ++i) {
      let val = _Math.abs(me[offset + i]);
      if (val > maxVal) {
        maxIdx = i;
        maxVal = val;
      }
    }
    return maxIdx;
  }
docs: Finds the largest element in the matrix column.
  @memberof Helpers
  @param {Matrix2|Matrix3|Matrix4} M The matrix.
  @param {number} i The column index.
  @returns {number} The row index of the column's largest element.