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pop_firws.m
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pop_firws.m
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% pop_firws() - Filter data using windowed sinc FIR filter
%
% Usage:
% >> [EEG, com, b] = pop_firws(EEG); % pop-up window mode
% >> [EEG, com, b] = pop_firws(EEG, 'key1', value1, 'key2', ...
% value2, 'keyn', valuen);
%
% Inputs:
% EEG - EEGLAB EEG structure
% 'fcutoff' - vector or scalar of cutoff frequency/ies (-6 dB; Hz)
% 'forder' - scalar filter order. Mandatory even
%
% Optional inputs:
% 'ftype' - char array filter type. 'bandpass', 'highpass',
% 'lowpass', or 'bandstop' {default 'bandpass' or
% 'lowpass', depending on number of cutoff frequencies}
% 'wtype' - char array window type. 'rectangular', 'hann',
% 'hamming', 'blackman', or 'kaiser' {default 'hamming'}
% 'warg' - scalar kaiser beta
% 'minphase' - scalar boolean minimum-phase converted causal filter
% {default false}
% 'usefftfilt' - scalar boolean use fftfilt frequency domain filtering
% {default false}
% 'plotfresp' - scalar boolean plot filter responses {default false}
%
% Outputs:
% EEG - filtered EEGLAB EEG structure
% com - history string
% b - filter coefficients
%
% Note:
% Window based filters' transition band width is defined by filter
% order and window type/parameters. Stopband attenuation equals
% passband ripple and is defined by the window type/parameters. Refer
% to table below for typical parameters. (Windowed sinc) symmetric FIR
% filters have linear phase and can be made zero phase (non-causal) by
% shifting the data by the filters group delay (what firfilt does by
% default). Pi phase jumps noticable in the phase reponse reflect a
% negative frequency response and only occur in the stopband. pop_firws
% also allows causal filtering with minimum-phase (non-linear!) converted
% filter coefficients with similar properties. Non-linear causal
% filtering is NOT recommended for most use cases.
%
% Beta Max stopband Max passband Max passband Transition width Mainlobe width
% attenuation deviation ripple (dB) (normalized freq) (normalized rad freq)
% (dB)
% Rectangular -21 0.0891 1.552 0.9 / m* 4 * pi / m
% Hann -44 0.0063 0.109 3.1 / m 8 * pi / m
% Hamming -53 0.0022 0.038 3.3 / m 8 * pi / m
% Blackman -74 0.0002 0.003 5.5 / m 12 * pi / m
% Kaiser 5.653 -60 0.001 0.017 3.6 / m
% Kaiser 7.857 -80 0.0001 0.002 5.0 / m
% * m = filter order
%
% Author: Andreas Widmann, University of Leipzig, 2005
%
% See also:
% firfilt, firws, pop_firwsord, pop_kaiserbeta, plotfresp, windows
%123456789012345678901234567890123456789012345678901234567890123456789012
% Copyright (C) 2005 Andreas Widmann, University of Leipzig, widmann@uni-leipzig.de
%
% 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 2 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, write to the Free Software
% Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
function [EEG, com, b] = pop_firws(EEG, varargin)
com = '';
if nargin < 1
help pop_firws;
return;
end
if isempty(EEG.data)
error('Cannot process empty dataset');
end
if nargin < 2
drawnow;
ftypes = {'bandpass', 'highpass', 'lowpass', 'bandstop'};
ftypesStr = {'Bandpass', 'Highpass', 'Lowpass', 'Bandstop'};
wtypes = {'rectangular', 'hann', 'hamming', 'blackman', 'kaiser'};
wtypesStr = {'Rectangular (PB dev=0.089, SB att=-21dB)', 'Hann (PB dev=0.006, SB att=-44dB)', 'Hamming (PB dev=0.002, SB att=-53dB)', 'Blackman (PB dev=0.0002, SB att=-74dB)', 'Kaiser'};
uigeom = {[1 0.75 0.75] [1 0.75 0.75] 1 [1 0.75 0.75] [1 0.75 0.75] [1 0.75 0.75] [1 1.5] [1 1.5] 1 [1 0.75 0.75]};
uilist = {{'Style' 'text' 'String' 'Cutoff frequency(ies) [hp lp] (-6 dB; Hz):'} ...
{'Style' 'edit' 'String' '' 'Tag' 'fcutoffedit'} {} ...
{'Style' 'text' 'String' 'Filter type:'} ...
{'Style' 'popupmenu' 'String' ftypesStr 'Tag' 'ftypepop'} {} ...
{} ...
{'Style' 'text' 'String' 'Window type:'} ...
{'Style' 'popupmenu' 'String' wtypesStr 'Tag' 'wtypepop' 'Value' 3 'Callback' 'temp = {''off'', ''on''}; set(findobj(gcbf, ''-regexp'', ''Tag'', ''^warg''), ''Enable'', temp{double(get(gcbo, ''Value'') == 5) + 1}), set(findobj(gcbf, ''Tag'', ''wargedit''), ''String'', '''')'} {} ...
{'Style' 'text' 'String' 'Kaiser window beta:' 'Tag' 'wargtext' 'Enable' 'off'} ...
{'Style' 'edit' 'String' '' 'Tag' 'wargedit' 'Enable' 'off'} ...
{'Style' 'pushbutton' 'String' 'Estimate' 'Tag' 'wargpush' 'Enable' 'off' 'Callback' @comwarg} ...
{'Style' 'text' 'String' 'Filter order (mandatory even):'} ...
{'Style' 'edit' 'String' '' 'Tag' 'forderedit'} ...
{'Style' 'pushbutton' 'String' 'Estimate' 'Callback' {@comforder, wtypes, EEG.srate}} ...
{} {'Style' 'checkbox', 'String', 'Use minimum-phase converted causal filter (non-linear!)', 'Tag' 'minphase', 'Value', 0} ...
{} {'Style' 'checkbox', 'String', 'Use frequency domain filtering (faster for high filter orders > ~2000)', 'Tag' 'usefftfilt', 'Value', 0} ...
{'Style' 'edit' 'Tag' 'devedit' 'Visible' 'off'} ...
{} {} {'Style' 'pushbutton' 'String', 'Plot filter responses' 'Callback' {@comfresp, wtypes, ftypes, EEG.srate}}};
result = inputgui(uigeom, uilist, 'pophelp(''pop_firws'')', 'Filter the data -- pop_firws()');
if isempty(result), return; end
Args = {};
if ~isempty(result{1})
Args = [Args {'fcutoff'} {str2num(result{1})}];
end
Args = [Args {'ftype'} ftypes(result{2})];
Args = [Args {'wtype'} wtypes(result{3})];
if ~isempty(result{4})
Args = [Args {'warg'} {str2double(result{4})}];
end
if ~isempty(result{5})
Args = [Args {'forder'} {str2double(result{5})}];
end
Args = [Args {'minphase'} result{6}];
Args = [Args {'usefftfilt'} result{7}];
else
Args = varargin;
end
% Convert args to structure
Args = struct(Args{:});
c = parseargs(Args, EEG.srate);
b = firws(c{:});
% Defaults
if ~isfield(Args, 'minphase') || isempty(Args.minphase)
Args.minphase = 0;
end
if ~isfield(Args, 'usefftfilt') || isempty(Args.usefftfilt)
Args.usefftfilt = 0;
end
if ~isfield(Args, 'plotfresp') || isempty(Args.plotfresp)
Args.plotfresp = 0;
end
% Prepare reporting
if ~isfield(Args, 'ftype') || isempty(Args.ftype)
if length(Args.fcutoff) == 1, ftype = 'lowpass'; else ftype = 'bandpass'; end
else
ftype = Args.ftype;
end
if Args.minphase, dir = 'onepass-minphase'; else dir = 'onepass-zerophase'; end
if ~isfield(Args, 'wtype') || isempty(Args.wtype), Args.wtype = 'hamming'; else wtype = Args.wtype; end
if strcmp(wtype, 'kaiser'), dev = invkaiserbeta(Args.warg); else dev = []; end
[df, dev] = invfirwsord(wtype, EEG.srate, Args.forder, dev);
% Check for low filter order and report
maxDf = min( [ Args.fcutoff * 2, ( EEG.srate / 2 - Args.fcutoff ) * 2, diff( sort( Args.fcutoff ) ) ] );
if df > maxDf
nOpt = firwsord(wtype, EEG.srate, maxDf, dev);
warning('firfilt:filterOrderLow', 'Filter order too low. For better results a minimum filter order of %d is recommended. Effective cutoff frequency might deviate from requested cutoff frequency.', nOpt)
firfiltreport('func', mfilename, 'family', [wtype '-windowed sinc FIR'], 'type', ftype, 'dir', dir, 'order', Args.forder)
else
firfiltreport('func', mfilename, 'family', [wtype '-windowed sinc FIR'], 'type', ftype, 'dir', dir, 'order', Args.forder, 'fs', EEG.srate, 'fc', Args.fcutoff, 'df', df, 'pbdev', dev, 'sbatt', dev)
end
% Filter
if Args.minphase
b = minphaserceps(b);
Args.causal = 1;
else
Args.causal = 0;
end
if Args.minphase || Args.usefftfilt % New code path
EEG = firfiltsplit(EEG, b, Args.causal, Args.usefftfilt);
else % Old code path
EEG = firfilt(EEG, b);
end
% Plot filter responses
if Args.plotfresp
plotfresp(b, 1, [], EEG.srate, dir);
end
% History string
com = sprintf('%s = pop_firws(%s', inputname(1), inputname(1));
for c = fieldnames(Args)'
if ischar(Args.(c{:}))
com = [com sprintf(', ''%s'', ''%s''', c{:}, Args.(c{:}))];
else
com = [com sprintf(', ''%s'', %s', c{:}, mat2str(Args.(c{:})))];
end
end
com = [com ');'];
% Convert structure args to cell array firws parameters
function c = parseargs(Args, srate)
% Filter order and cutoff frequencies
if ~isfield(Args, 'fcutoff') || ~isfield(Args, 'forder') || isempty(Args.fcutoff) || isempty(Args.forder)
error('Not enough input arguments.');
end
c = [{Args.forder} {sort(Args.fcutoff / (srate / 2))}]; % Sorting and normalization
% Filter type
if isfield(Args, 'ftype') && ~isempty(Args.ftype)
if (strcmpi(Args.ftype, 'bandpass') || strcmpi(Args.ftype, 'bandstop')) && length(Args.fcutoff) ~= 2
error('Not enough input arguments.');
elseif (strcmpi(Args.ftype, 'highpass') || strcmpi(Args.ftype, 'lowpass')) && length(Args.fcutoff) ~= 1
error('Too many input arguments.');
end
switch Args.ftype
case 'bandstop'
c = [c {'stop'}];
case 'highpass'
c = [c {'high'}];
end
end
% Window type
if isfield(Args, 'wtype') && ~isempty(Args.wtype)
if strcmpi(Args.wtype, 'kaiser')
if isfield(Args, 'warg') && ~isempty(Args.warg)
c = [c {windows(Args.wtype, Args.forder + 1, Args.warg)'}];
else
error('Not enough input arguments.');
end
else
c = [c {windows(Args.wtype, Args.forder + 1)'}];
end
end
% Callback estimate Kaiser beta
function comwarg(varargin)
[warg, dev] = pop_kaiserbeta;
set(findobj(gcbf, 'Tag', 'wargedit'), 'String', warg);
set(findobj(gcbf, 'Tag', 'devedit'), 'String', dev);
% Callback estimate filter order
function comforder(obj, evt, wtypes, srate)
wtype = wtypes{get(findobj(gcbf, 'Tag', 'wtypepop'), 'Value')};
dev = get(findobj(gcbf, 'Tag', 'devedit'), 'String');
[forder, dev] = pop_firwsord(wtype, srate, [], dev);
set(findobj(gcbf, 'Tag', 'forderedit'), 'String', forder);
set(findobj(gcbf, 'Tag', 'devedit'), 'String', dev);
% Callback plot filter responses
function comfresp(obj, evt, wtypes, ftypes, srate)
Args.fcutoff = str2num(get(findobj(gcbf, 'Tag', 'fcutoffedit'), 'String'));
Args.ftype = ftypes{get(findobj(gcbf, 'Tag', 'ftypepop'), 'Value')};
Args.wtype = wtypes{get(findobj(gcbf, 'Tag', 'wtypepop'), 'Value')};
Args.warg = str2num(get(findobj(gcbf, 'Tag', 'wargedit'), 'String'));
Args.forder = str2double(get(findobj(gcbf, 'Tag', 'forderedit'), 'String'));
Args.minphase = get(findobj(gcbf, 'Tag', 'minphase'), 'Value');
c = parseargs(Args, srate);
b = firws(c{:});
if Args.minphase
b = minphaserceps(b);
dir = 'onepass-minphase';
else
dir = 'onepass-zerophase';
end
H = findobj('Tag', 'plotfiltresp', 'type', 'figure');
if ~isempty(H)
figure(H);
else
H = figure;
set(H, 'color', [.93 .96 1], 'Tag', 'plotfiltresp');
end
plotfresp(b, 1, [], srate, dir);