code: function baseTranspose(matrix) {
    return map(head(matrix), function (column, index) {
      return map(matrix, function (row) {
        return row[index];
      });
    });
  }
docs: Base matrix transpose. Turns an n by m matrix into m by n.
  @private
  @param {Array} matrix - Two-dimensional array (n by m).
  @returns {Array} Returns m by n matrix.