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: amutual.m
    path of file: ./repos/hctsa/Toolboxes/OpenTSTOOL/tstoolbox/@signal
    
    the code of the file until where you have to start completion: function rs = amutual(s, maxtau, bins)

%tstoolbox/@signal/amutual
%   Syntax:
%     * amutual(s, maxtau, bins)
%
%   Input arguments:
%     * maxtau - maximal delay (should be much smaller than the lenght of
%       s) (optional)

    
function rs = amutual(s, maxtau, bins)

%tstoolbox/@signal/amutual
%   Syntax:
%     * amutual(s, maxtau, bins)
%
%   Input arguments:
%     * maxtau - maximal delay (should be much smaller than the lenght of
%       s) (optional)
%     * bins - number of bins used for histogram calculation (optional)
%
%   Auto mutual information function for real scalar signals, can be used
%   to determine a proper delay time for time-delay reconstruction. The
%   default value for maxtau is 25% of the input signal's length. The
%   default number of bins is 128.
%
%               [missing equation, see html/pdf documentation]
%
% Copyright 1997-2001 DPI Goettingen, License http://www.physik3.gwdg.de/tstool/gpl.txt

narginchk(1,3);

if (ndim(s) > 1) | (~isreal(data(s)))
    error('Input signal must be a scalar time series');
end