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: randnfundisk.m
    path of file: ./repos/chebfun
    
    the code of the file until where you have to start completion: function f = randnfundisk(lambda)
%RANDNFUNDISK   Smooth random function on the unit disk
%   F = RANDNFUNDISK(LAMBDA) returns a DISKFUN of maximum
%   frequency about 2pi/LAMBDA and standard normal distribution N(0,1)
%   at each point.  F is obtained by restricting output of RANDNFUN2
%   to the unit disk.
%
%   RANDNFUNDISK() uses the default value LAMBDA = 1.

    
function f = randnfundisk(lambda)
%RANDNFUNDISK   Smooth random function on the unit disk
%   F = RANDNFUNDISK(LAMBDA) returns a DISKFUN of maximum
%   frequency about 2pi/LAMBDA and standard normal distribution N(0,1)
%   at each point.  F is obtained by restricting output of RANDNFUN2
%   to the unit disk.
%
%   RANDNFUNDISK() uses the default value LAMBDA = 1.
%
% Examples:
%
%   f = randnfundisk(0.5); plot(f)
%   colormap([0 0 0; 1 0 0]), caxis(norm(caxis,inf)*[-1 1]), axis off
%
% See also RANDNFUN, RANDNFUN2, RANDNFUNSPHERE.

% Copyright 2017 by The University of Oxford and The Chebfun Developers. 
% See http://www.chebfun.org/ for Chebfun information.

if nargin == 0
    lambda = 1;
end