statistic
Return UV plane visibility statistics.
EXAMPLE
-------

 0>print uvstat(rms)
 0.333969 
 0>
 0>print uvstat(chisq)
 1.07537 
 0>
 0>print uvstat(nvis)
 10756 
 0>

PARAMETERS
----------

statistic  -  The name of the statistic wanted. Recognised names are:

               rms   -   The root-mean-square difference between observed
                         and model visibilities (Jy).
               chisq -   The reduced chi-squared fit between the
                         observed and model visibilities.
               nvis  -   The number of un-flagged visibilities.

CONTEXT
-------
This function provides access to a few statistics relating model and
observed visibilities in the UV plane. The return value may be used in
expressions, and thus may be used in automatic mapping procedures.

SIDE EFFECTS
------------
The tentative model will be established in the UV plane if not already
there. This in turn will force difmap to re-invert the data before the
next operation that involves the current map.

RELATED COMMANDS
----------------
imstat - Return image plane map statistics.
