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: filt1.m
    path of file: ./repos/CDT/cdt
    
    the code of the file until where you have to start completion: function [yf,filtb,filta] = filt1(filtertype,y,varargin) 
% filt1 applies a zero-phase butterworth filter. (Requires Matlab's Signal
% Processing Toolbox.)
% 
%% Syntax
% 
%  yf = filt1(filtertype,y,'fc',Fc)
%  yf = filt1(filtertype,y,'Tc',Tc)
%  yf = filt1(filtertype,y,'lambdac',lambdac)
%  yf = filt1(...,'fs',Fs)
%  yf = filt1(...,'x',x)
%  yf = filt1(...,'Ts',Ts)
%  yf = filt1(...,'order',FilterOrder)
%  yf = filt1(...,'dim',dim)
%  [yf,filtb,filta] = filt1(...)
% 
%% Description
% 
% yf = filt1(filtertype,y,'fc',Fc) filters 1D signal y
% using a specified filtertype and cutoff frequency Fc. For 
% high-pass or low-pass filters Fc must be a scalar. For band-
% pass and band-stop filters Fc must be a two-element array. The 
% filtertype can be 
% 
%   * 'hp' high-pass with scalar cutoff frequency Fc
%   * 'lp' low-pass with scalar cutoff frequency Fc
%   * 'bp' band-pass with two-element cutoff frequencies Fc
%   * 'bs' band-stop with two-element cutoff frequencies Fc 
% 
% |yf = filt1(filtertype,y,'Tc',Tc)| specifies cutoff period(s)
% rather than cutoff frequencies. This syntax assumes T = 1/f and is exactly
% the same as the 'lambdac' option, but perhaps a little more intuitive for
% working with time series. 
% 
% yf = filt1(filtertype,y,'lambdac',lambdac) specifies cutoff
% wavelength(s) rather than cutoff frequencies.  This syntax assumes
% lambda = 1/f. 
% 
% yf = filt1(...,'fs',Fs) specifies a sampling frequency Fs. 
% If neither 'fs', 'x', nor 'Ts' are specified, Fs = 1 is assumed.    
% 
% yf = filt1(...,'x',x) specifies a vector of  monotonically-
% increasing, equally-spaced sampling times or x locations corresponding
% to y, which is used to determine sampling frequency. If neither 'fs', 
% 'x', nor 'Ts' are specified, Fs = 1 is assumed.  
% 
% yf = filt1(...,'Ts',Ts) specifies a sampling period or sampling distance
% such that Fs = 1/Ts. If neither 'fs', 'x', nor 'Ts' are specified, 
% Fs = 1 is assumed.    
% 
% yf = filt1(...,'order',FilterOrder) specifies the order (sometimes 
% called rolloff) of the Butterworth filter. If unspecified, 
% FilterOrder = 1 is assumed. 
% 
% yf = filt1(...,'dim',dim) specifies a dimension along which to operate. 
% By default, filt1 operates along the first nonsingleton dimension for 1D or 
% 2D arrays, but operates down dimension 3 for 3D gridded datasets. 
% 
% [yf,filtb,filta] = filt1(...) also returns the filter numerator 
% filta and denominator filtb. 
% 
%% Example 
% For examples, type 
% 
%  cdt filt1
% 
%% Author Info
% The filt1 function was written by Chad A. Greene of the University of
% Texas at Austin's Institute for Geophysics (UTIG), October 2015. 
% http://www.chadagreene.com
% 
% See also butter, filtfilt, and scatstat1. 

%% Initial error checks: 

assert(license('test','signal_toolbox')==1,'The filt1 function requires Matlab''s Signal Processing Toolbox.')
assert(nargin>3,'Not enough input arguments.') 
assert(sum(strcmpi({'hp';'lp';'bp';'bs';'high';'low';'bandpass';'stop'},filtertype))==1,'Filter type must be ''hp'', ''lp'', or ''bp''.'),
assert(sum([strcmpi(varargin,'fc') strcmpi(varargin,'lambdac') strcmpi(varargin,'Tc')])==1,'Must declare a cutoff frequency (or frequencies) ''fc'',  cutoff wavelength(s) ''lambdac'', or cutoff period(s) ''Tc''.')

%% Define defaults: 

order = 1; 
Fs = 1; 

%% Parse Inputs: 

% Replace filtertype string if necessary: 
filtertype = strrep(filtertype,'hp','high'); 
filtertype = strrep(filtertype,'lp','low'); 
filtertype = strrep(filtertype,'bp','bandpass'); 
filtertype = strrep(filtertype,'bs','stop'); 

% Is a sampling frequency defined? 

    
function [yf,filtb,filta] = filt1(filtertype,y,varargin) 
% filt1 applies a zero-phase butterworth filter. (Requires Matlab's Signal
% Processing Toolbox.)
% 
%% Syntax
% 
%  yf = filt1(filtertype,y,'fc',Fc)
%  yf = filt1(filtertype,y,'Tc',Tc)
%  yf = filt1(filtertype,y,'lambdac',lambdac)
%  yf = filt1(...,'fs',Fs)
%  yf = filt1(...,'x',x)
%  yf = filt1(...,'Ts',Ts)
%  yf = filt1(...,'order',FilterOrder)
%  yf = filt1(...,'dim',dim)
%  [yf,filtb,filta] = filt1(...)
% 
%% Description
% 
% yf = filt1(filtertype,y,'fc',Fc) filters 1D signal y
% using a specified filtertype and cutoff frequency Fc. For 
% high-pass or low-pass filters Fc must be a scalar. For band-
% pass and band-stop filters Fc must be a two-element array. The 
% filtertype can be 
% 
%   * 'hp' high-pass with scalar cutoff frequency Fc
%   * 'lp' low-pass with scalar cutoff frequency Fc
%   * 'bp' band-pass with two-element cutoff frequencies Fc
%   * 'bs' band-stop with two-element cutoff frequencies Fc 
% 
% |yf = filt1(filtertype,y,'Tc',Tc)| specifies cutoff period(s)
% rather than cutoff frequencies. This syntax assumes T = 1/f and is exactly
% the same as the 'lambdac' option, but perhaps a little more intuitive for
% working with time series. 
% 
% yf = filt1(filtertype,y,'lambdac',lambdac) specifies cutoff
% wavelength(s) rather than cutoff frequencies.  This syntax assumes
% lambda = 1/f. 
% 
% yf = filt1(...,'fs',Fs) specifies a sampling frequency Fs. 
% If neither 'fs', 'x', nor 'Ts' are specified, Fs = 1 is assumed.    
% 
% yf = filt1(...,'x',x) specifies a vector of  monotonically-
% increasing, equally-spaced sampling times or x locations corresponding
% to y, which is used to determine sampling frequency. If neither 'fs', 
% 'x', nor 'Ts' are specified, Fs = 1 is assumed.  
% 
% yf = filt1(...,'Ts',Ts) specifies a sampling period or sampling distance
% such that Fs = 1/Ts. If neither 'fs', 'x', nor 'Ts' are specified, 
% Fs = 1 is assumed.    
% 
% yf = filt1(...,'order',FilterOrder) specifies the order (sometimes 
% called rolloff) of the Butterworth filter. If unspecified, 
% FilterOrder = 1 is assumed. 
% 
% yf = filt1(...,'dim',dim) specifies a dimension along which to operate. 
% By default, filt1 operates along the first nonsingleton dimension for 1D or 
% 2D arrays, but operates down dimension 3 for 3D gridded datasets. 
% 
% [yf,filtb,filta] = filt1(...) also returns the filter numerator 
% filta and denominator filtb. 
% 
%% Example 
% For examples, type 
% 
%  cdt filt1
% 
%% Author Info
% The filt1 function was written by Chad A. Greene of the University of
% Texas at Austin's Institute for Geophysics (UTIG), October 2015. 
% http://www.chadagreene.com
% 
% See also butter, filtfilt, and scatstat1. 

%% Initial error checks: 

assert(license('test','signal_toolbox')==1,'The filt1 function requires Matlab''s Signal Processing Toolbox.')
assert(nargin>3,'Not enough input arguments.') 
assert(sum(strcmpi({'hp';'lp';'bp';'bs';'high';'low';'bandpass';'stop'},filtertype))==1,'Filter type must be ''hp'', ''lp'', or ''bp''.'),
assert(sum([strcmpi(varargin,'fc') strcmpi(varargin,'lambdac') strcmpi(varargin,'Tc')])==1,'Must declare a cutoff frequency (or frequencies) ''fc'',  cutoff wavelength(s) ''lambdac'', or cutoff period(s) ''Tc''.')

%% Define defaults: 

order = 1; 
Fs = 1; 

%% Parse Inputs: 

% Replace filtertype string if necessary: 
filtertype = strrep(filtertype,'hp','high'); 
filtertype = strrep(filtertype,'lp','low'); 
filtertype = strrep(filtertype,'bp','bandpass'); 
filtertype = strrep(filtertype,'bs','stop'); 

% Is a sampling frequency defined? 
tmp = strcmpi(varargin,'fs'); 
if any(tmp) 
    Fs = varargin{find(tmp)+1}; 
end