% Purpose
%    sets (define) a variable.
%
% Synopsis
%    mexeps('setvar',varcode)
%    mexeps('setvar',varcode,sname,lname,gname,frmt,units)
%
% Description
%    It sets variable information before you writes out that 
%    variable to a data file.   The variable is refered to by
%    its variable code, varcode.  If varcode > 0 and it is 
%    defined in epic.key file, then rest of the input arguments
%    (short name, long name, generic name, format and units) 
%    can be omitted; if varcode is not defined in epic.key file,
%    these arugments must be given. 
%
% Examples
%
%    new_id = -1;
%    sname = 'new_var';          % set new short name
%    lname = 'long new_var';     % set new long name
%    gname = 'generic new_var';  % set new generic name
%    frmt = ' ';                 % set new format
%    units = 'new units';        % set new units
%
%    mexeps('setvar',new_id,sname,lname,gname,frmt,units);
%
% See Also
%    putvar, putaxis, puttaxis
%