def polymulx(c):
<EOL>[c] = pu.as_series([c])<EOL>if len(c) == <NUM_LIT:1> and c[<NUM_LIT:0>] == <NUM_LIT:0>:<EOL><INDENT>return c<EOL><DEDENT>prd = np.empty(len(c) + <NUM_LIT:1>, dtype=c.dtype)<EOL>prd[<NUM_LIT:0>] = c[<NUM_LIT:0>]*<NUM_LIT:0><EOL>prd[<NUM_LIT:1>:] = c<EOL>return prd<EOL>
Multiply a polynomial by x.

    Multiply the polynomial `c` by x, where x is the independent
    variable.


    Parameters
    ----------
    c : array_like
        1-D array of polynomial coefficients ordered from low to
        high.

    Returns
    -------
    out : ndarray
        Array representing the result of the multiplication.

    Notes
    -----

    .. versionadded:: 1.5.0