<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_minimum(min_freq=None, min_time=None, min_off=None, min_res=None, min_angle=None):
 r""" Set minimum values of parameters. The given parameters are set to its minimum value if they are smaller. Parameters min_freq : float, optional Minimum frequency [Hz] (default 1e-20 Hz). min_time : float, optional Minimum time [s] (default 1e-20 s). min_off : float, optional Minimum offset [m] (default 1e-3 m). Also used to round src- & rec-coordinates. min_res : float, optional Minimum horizontal and vertical resistivity [Ohm.m] (default 1e-20). min_angle : float, optional Minimum angle [-] (default 1e-10). Note ---- set_minimum and get_minimum are derived after set_printoptions and get_printoptions from arrayprint.py in numpy. """


    global _min_freq, _min_time, _min_off, _min_res, _min_angle

    if min_freq is not None:
        _min_freq = min_freq
    if min_time is not None:
        _min_time = min_time
    if min_off is not None:
        _min_off = min_off
    if min_res is not None:
        _min_res = min_res
    if min_angle is not None:
        _min_angle = min_angle