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# brainstorm_filt

## (Toolbox/brainstorm_filt.m in BrainStorm 2.0 (Alpha))

### Function Synopsis

    [smoothdata,filtwts] = brainstorm_filt(data,srate,locutoff,hicutoff,epochframes,filtorder)

### Help Text

    BRAINSTORM_FILT - Zero-phase filter dedicated to multi-channel MEG and EEG data
     function [smoothdata,filtwts] = brainstorm_filt(data,srate,locutoff,hicutoff,epochframes,filtorder)
    Zero-phase filter dedicated to multi-channel MEG and EEG data
    Necessitates the Matlab Signal Processing Toolbox

### Cross-Reference Information

This function calls

    bst_message_window                 C:\BrainStorm_2001\Toolbox\bst_message_window.m

This function is called by

    dataplot_cb                        C:\BrainStorm_2001\Toolbox\dataplot_cb.m
    manage_corticalscouts              C:\BrainStorm_2001\Toolbox\manage_corticalscouts.m

### Listing of function C:\BrainStorm_2001\Toolbox\brainstorm_filt.m

    function [smoothdata,filtwts] = brainstorm_filt(data,srate,locutoff,hicutoff,epochframes,filtorder)
    %BRAINSTORM_FILT - Zero-phase filter dedicated to multi-channel MEG and EEG data
    % function [smoothdata,filtwts] = brainstorm_filt(data,srate,locutoff,hicutoff,epochframes,filtorder)
    %Zero-phase filter dedicated to multi-channel MEG and EEG data
    %Necessitates the Matlab Signal Processing Toolbox

    %<autobegin> ---------------------- 09-Jul-2004 22:16:45 -----------------------
    % --------- Automatically Generated Comments Block Using AUTO_COMMENTS ---------
    %
    % CATEGORY: Utility - Numeric
    %
    % Alphabetical list of external functions (non-Matlab):
    %   toolbox\bst_message_window.m
    %
    % At Check-in: $Author: Mosher $  $Revision: 19 $  $Date: 7/09/04 8:42p $
    %
    % This software is part of BrainStorm Toolbox Version 2.0 (Alpha) 09-Jul-2004
    %
    % Principal Investigators and Developers:
    % ** Richard M. Leahy, PhD, Signal & Image Processing Institute,
    %    University of Southern California, Los Angeles, CA
    % ** John C. Mosher, PhD, Biophysics Group,
    %    Los Alamos National Laboratory, Los Alamos, NM
    % ** Sylvain Baillet, PhD, Cognitive Neuroscience & Brain Imaging Laboratory,
    %    CNRS, Hopital de la Salpetriere, Paris, France
    %
    % See BrainStorm website at http://neuroimage.usc.edu for further information.
    %
    % Copyright (c) 2004 BrainStorm by the University of Southern California
    % This software distributed  under the terms of the GNU General Public License
    % as published by the Free Software Foundation. Further details on the GPL
    % license can be found at http://www.gnu.org/copyleft/gpl.html .
    %
    % FOR RESEARCH PURPOSES ONLY. THE SOFTWARE IS PROVIDED "AS IS," AND THE
    % UNIVERSITY OF SOUTHERN CALIFORNIA AND ITS COLLABORATORS DO NOT MAKE ANY
    % WARRANTY, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF
    % MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, NOR DO THEY ASSUME ANY
    % LIABILITY OR RESPONSIBILITY FOR THE USE OF THIS SOFTWARE.
    %<autoend> ------------------------ 09-Jul-2004 22:16:45 -----------------------

    % Author: Sylvain Baillet, Ph.D.
    % ----------------------------- Script History ---------------------------------
    % JCM 19-May-2004  Comments cleaning
    % ----------------------------- Script History ---------------------------------

    if nargin<4
        help brainstorm_filt
        return
    end

    if ~exist('firls')
        bst_message_window('\n This filter requires the Matlab Signal Processing toolbox.\ ***n\n');
        errordlg('This filter requires the Matlab Signal Processing toolbox')
        return
    end

    [chans frames] = size(data);
    if chans > 1 & frames == 1,
        help brainstorm_filt
        errordlg('Input data should be a row vector.\n\n');
        return
    end
    nyq            = srate*0.5;  % Nyquist frequency
    MINFREQ = 0.1/nyq;

    minfac         = 3;    % this many (lo)cutoff-freq cycles in filter
    min_filtorder  = 15;   % minimum filter length
    trans          = 0.25; % fractional width of transition zones

    if locutoff>0 & hicutoff > 0 & locutoff > hicutoff,
        bst_message_window('\n locutoff cannot be larger than hicutoff\n');
        help brainstorm_filt
        return
    end
    if locutoff < 0 | hicutoff < 0,
        help brainstorm_filt
        return
    end

    if locutoff>nyq,
        bst_message_window(sprintf('\n Locutoff freq cannot be larger than srate/2.\n.',nyq));
        help brainstorm_filt
        return
    end

    if hicutoff>=nyq
        hicutoff = 0;
    end

    if nargin<6
        filtorder = 0;
    end

    if filtorder==0,
        if locutoff>0,
            filtorder = minfac*fix(srate/locutoff);
        elseif hicutoff>0,
            filtorder = minfac*fix(srate/hicutoff);
        end

        if filtorder < min_filtorder
            filtorder == min_filtorder;
        end
    end

    if nargin<5
        epochframes = 0;
    end
    if epochframes ==0,
        epochframes = frames;    % default
    end
    epochs = fix(frames/epochframes);
    if epochs*epochframes ~= frames,
        %fprintf('brainstorm_filt(): epochframes does not divide frames.\n');
        return
    end

    if filtorder*3 > epochframes,   % Matlab filtfilt() restriction
        errordlg('Number of time samples is too small to apply this filter.\n');
        return
    end

    if locutoff > 0 & hicutoff > 0,    % bandpass filter
        bst_message_window(sprintf('Filtering...%d-point bandpass filter.\n',filtorder));
        f=[MINFREQ (1-trans)*locutoff/nyq locutoff/nyq hicutoff/nyq (1+trans)*hicutoff/nyq 1];
        m=[0       0                      1            1            0                      0];
    elseif locutoff > 0                % highpass filter
        if locutoff/nyq < MINFREQ
            help brainstorm_filt
            errodlg('Highpass cut-off freq must be > %g Hz\n\n',MINFREQ*nyq);
            return
        end
        bst_message_window(sprintf('Filtering...%d-point highpass filter.\n',filtorder));
        f=[MINFREQ locutoff*(1-trans)/nyq locutoff/nyq 1];
        m=[   0             0                   1      1];
    elseif hicutoff > 0                %  lowpass filter
        if hicutoff/nyq < MINFREQ
            help brainstorm_filt
            errodlg('Lowpass cut-off freq must be > %g Hz\n\n',MINFREQ*nyq);
            return
        end
        bst_message_window(sprintf('Filtering...%d-point lowpass filter.\n',filtorder));
        f=[MINFREQ hicutoff/nyq hicutoff*(1+trans)/nyq 1];
        m=[     1           1              0                 0];
    else
        errordlg(sprintf(...
            'High or low cut-off frequency might be larger that Nyquist largest admissible frequency value: %3.2f Hz.',nyq),...
            'Error in specifying cut-off frequencies')
        return
    end

    filtwts = firls(filtorder,f,m); % get FIR filter coefficients

    smoothdata = zeros(chans,frames);
    for e = 1:epochs                % filter each epoch, channel
        for c=1:chans
            smoothdata(c,(e-1)*epochframes+1:e*epochframes) ...
                = filtfilt(filtwts,1,data(c,(e-1)*epochframes+1:e*epochframes));
        end
    end

Produced by color_mat2html, a customized BrainStorm 2.0 (Alpha) version of mat2html on Tue Nov 2 16:17:59 2004
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