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function gout=firfilter(name,M,varargin)
%-*- texinfo -*-
%@deftypefn {Function} firfilter
%@verbatim
%FIRFILTER Construct an FIR filter
% Usage: g=firfilter(name,M);
% g=firfilter(name,M,...);
%
% FIRFILTER(name,M) creates an FIR filter of length M. This is
% exactly the same as calling FIRWIN. The name must be one of the
% accepted window types of FIRWIN.
%
% FIRFILTER(name,M,fc) constructs a filter with a centre
% frequency of fc measured in normalized frequencies.
%
% If one of the inputs is a vector, the output will be a cell array
% with one entry in the cell array for each element in the vector. If
% more input are vectors, they must have the same size and shape and the
% the filters will be generated by stepping through the vectors. This
% is a quick way to create filters for FILTERBANK and UFILTERBANK.
%
% FIRFILTER accepts the following optional parameters:
%
% 'fs',fs If the sampling frequency fs is specified then the length
% M is specified in seconds and the centre frequency
% fc in Hz.
%
% 'complex' Make the filter complex valued if the centre frequency
% is non-zero. This is the default.
%
% 'real' Make the filter real-valued if the centre frequency
% is non-zero.
%
% 'delay',d Set the delay of the filter. Default value is zero.
%
% 'causal' Create a causal filter starting at the first sample. If
% specified, this flag overwrites the delay setting.
%
% It is possible to normalize the impulse response of the filter by
% passing any of the flags from the NORMALIZE function. The default
% normalization is 'energy'.
%
% The filter can be used in the PFILT routine to filter a signal, or
% in can be placed in a cell-array for use with FILTERBANK or UFILTERBANK.
%
%@end verbatim
%@strong{Url}: @url{http://ltfat.github.io/doc/sigproc/firfilter.html}
%@seealso{blfilter, firwin, pfilt, filterbank}
%@end deftypefn
% Copyright (C) 2005-2016 Peter L. Soendergaard <peter@sonderport.dk>.
% This file is part of LTFAT version 2.3.1
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
% XXX Implement passing additional parameters to firwin
% Define initial value for flags and key/value pairs.
definput.import={'normalize'};
definput.importdefaults={'energy'};
definput.keyvals.delay=0;
definput.keyvals.fc=0;
definput.keyvals.fs=[];
definput.flags.delay={'delay','causal'};
definput.flags.real={'complex','real'};
[flags,kv]=ltfatarghelper({'fc'},definput,varargin);
[M,kv.fc,kv.delay]=scalardistribute(M,kv.fc,kv.delay);
if ~isempty(kv.fs)
M=round(M*kv.fs);
kv.fc=kv.fc/kv.fs*2;
end;
Nfilt=numel(M);
gout=cell(1,Nfilt);
for ii=1:Nfilt
g=struct();
if flags.do_causal
g.offset=0;
smallshift=0;
else
d=floor(kv.delay);
smallshift=d-floor(d);
g.offset=d-floor(M/2);
end;
g.h=fftshift(firwin(name,M(ii),'shift',smallshift(ii),flags.norm));
g.fc=kv.fc(ii);
g.realonly=flags.do_real;
g.fs=kv.fs;
gout{ii}=g;
end;
if Nfilt==1
gout=g;
end;
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