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# inorcol

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

### Function Synopsis

    [normeM] = inorcol(Mat)

### Help Text

    INORCOL - Compute the (pseudo)inverse of the column norms of matrix Mat
     function [normeM] = inorcol(Mat)
     normeM is a sparse diagonal matrix whose diagonal elements
      are the inverse of the corresponding column norm of matrix Mat.
      If a column is zero, then its inverse is set to zero as well.

### Cross-Reference Information

This function is called by

    bst_headmodeler                    C:\BrainStorm_2001\Toolbox\bst_headmodeler.m
    lcmvbf                             C:\BrainStorm_2001\Toolbox\lcmvbf.m
    manage_corticalscouts              C:\BrainStorm_2001\Toolbox\manage_corticalscouts.m
    minnorm                            C:\BrainStorm_2001\Toolbox\minnorm.m
    os_meg                             C:\BrainStorm_2001\Toolbox\os_meg.m
    sourceimaging                      C:\BrainStorm_2001\Toolbox\sourceimaging.m
    zscore_gui                         C:\BrainStorm_2001\Toolbox\zscore_gui.m

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

    function [normeM] = inorcol(Mat)
    %INORCOL - Compute the (pseudo)inverse of the column norms of matrix Mat
    % function [normeM] = inorcol(Mat)
    % normeM is a sparse diagonal matrix whose diagonal elements
    %  are the inverse of the corresponding column norm of matrix Mat.
    %  If a column is zero, then its inverse is set to zero as well.

    %<autobegin> ---------------------- 26-May-2004 11:30:45 -----------------------
    % --------- Automatically Generated Comments Block Using AUTO_COMMENTS ---------
    %
    % CATEGORY: Utility - Numeric
    %
    % At Check-in: $Author: Mosher $  $Revision: 14 $  $Date: 5/26/04 9:59a $
    %
    % This software is part of BrainStorm Toolbox Version 2.0 (Alpha) 24-May-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> ------------------------ 26-May-2004 11:30:45 -----------------------

    % ----------------------- History -----------------------------------
    % JCM 19-May-2003  Handling error case of zero column norm
    % ----------------------- History -----------------------------------

    cn = sqrt(sum(Mat.*Mat,1)'); % sum only the rows into a column vector
    Zero = max(cn)*eps; % relative concept of zero
    ndx = cn > Zero;
    cn(ndx) = 1 ./ cn(ndx); % zero values are kept zero for a pseudoinverse

    normeM = spdiags(cn,0,length(cn),length(cn));

    if(0) % old code
        tmp = speye(size(Mat,2));
        normeM = 1./sqrt(sum(Mat.*Mat))';
        normeM = spdiags(normeM,0,tmp);
    end

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