SPECIFY FREQUENCY

        SPECIFY FREQUENCY Arg [Keyword Value ...] [/FOR SicVariable]
    Modify the rest frequency(ies) and recompute the velocity scale accordingly.

    Arg is a number or scalar variable, it should contain the new rest frequency
    in  MHz.  In this mode, there may be other arguments to specify e.g. the VE-
    LOCITY or LINENAME.

    If it is the name of a SIC array variable, variable Arg must be a 1-D double
    precision array that contains frequencies  (in MHz) for every channel of the
    UV data to which it applies. This is by default the current UV data,  unless
    option   /FOR indicates another (UV-like) variable. This mode allows to han-
    dle irregular frequency sampling that occurs e.g. in JVLA data sets. No fur-
    ther argument is allowed in this mode.