You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: vscale.m
    path of file: ./repos/chebfun/@ballfun
    
    the code of the file until where you have to start completion: function V = vscale( F )
%VSCALE   Vertical scale of a BALLFUN.
% 
% VSCL = VSCALE(F) returns the vertial scale of a BALLFUN as determined
% by evaluating on a coarse tensor-product grid. 

    
function V = vscale( F )
%VSCALE   Vertical scale of a BALLFUN.
% 
% VSCL = VSCALE(F) returns the vertial scale of a BALLFUN as determined
% by evaluating on a coarse tensor-product grid. 

% Copyright 2019 by The University of Oxford and The Chebfun Developers.
% See http://www.chebfun.org/ for Chebfun information.

if isempty( F )
    V = [];
    return
end