Convert a floating-point location (float_row,float_col) in
        matrix coordinates to its corresponding location (x,y) in
        sheet coordinates.

        Valid for scalar or array float_row and float_col.

        Inverse of sheet2matrix().

def matrix2sheet(self,float_row,float_col):
        """
        Convert a floating-point location (float_row,float_col) in
        matrix coordinates to its corresponding location (x,y) in
        sheet coordinates.

        Valid for scalar or array float_row and float_col.

        Inverse of sheet2matrix().
        """
        xoffset = float_col*self.__xstep
        if isinstance(self.lbrt[0], datetime_types):
            xoffset = np.timedelta64(int(round(xoffset)), self._time_unit)
        x = self.lbrt[0] + xoffset
        yoffset = float_row*self.__ystep
        if isinstance(self.lbrt[3], datetime_types):
            yoffset = np.timedelta64(int(round(yoffset)), self._time_unit)
        y = self.lbrt[3] - yoffset
        return x, y