def atan(self, ir="", ia="", name="", facta="", **kwargs):
    """Forms the arctangent of a complex variable.

    APDL Command: ATAN

    Parameters
    ----------
    ir
        Arbitrary reference number assigned to the resulting variable (2 to
        NV [NUMVAR]).  If this number is the same as for a previously
        defined variable, the previously defined variable will be
        overwritten with this result.

    ia
        Reference number of the complex variable to be operated on.

    name
        Thirty-two character name for identifying the variable on the
        printout and displays.  Embedded blanks are compressed upon output.

    facta
        Scaling factor (positive or negative) applied to variable
        IA (defaults to 1.0).  Usually FACTA should be set to 1.
        FACTA may affect the position of the angle by a multiple
        of π, resulting in a quadrant change.

    Notes
    -----
    Forms the arctangent of a complex variable according to the
    operation:

    IR = ATAN(FACTA X b/a)

    where a and b are the real and imaginary parts, respectively,
    of the complex variable IA (which is of the form a + ib).  The
    arctangent represents the phase angle (in radians), and is
    valid only for a harmonic analysis (ANTYPE,HARMIC).

    Since the scaling factor is applied uniformly to b/a, applying
    any positive or negative scaling factor will not affect the
    size of the phase angle, with the exception that a negative
    scaling factor will change the results quadrant by : π.  The
    magnitude of a complex number is still obtained through the
    ABS command.  See POST26 - Data Operations in the Mechanical
    APDL Theory Reference for details.
    """
    command = f"ATAN,{ir},{ia},,,{name},,,{facta}"
    return self.run(command, **kwargs)