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# sensor_axial

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

### Function Synopsis

    [R,s] = sensor_axial(R1,baseline);

### Help Text

    SENSOR_AXIAL - Generate axial gradiometers
     function [R,s] = sensor_axial(R1,baseline);
     Given sensor sites in R1, generate
     axial point gradiometers in radial direction of R1 with baseline
     separations given in baseline.
     Each element of the vector baseline should give the total baseline
     distance from the R1 origin.

     For example, a BTi 37-channel first-order gradiometer pattern with a
     5 cm baseline would by simulated by
     R1 = sensor_ring(0.12,15*pi/180,4);  % generate sensor sites
     [R,s] = sensor_axial(R1,[0.05]);

     A second order gradiometer with a 4 cm baseline would be simulated by
     [R,s] = sensor_axial(R1,[0.04 0.08]);

     The first three columns of R and s will be the positions of the coils
       nearest the head.  The next three columns correspond to the second coil in
       each sensor.

     See also SENSOR_RING, SENSOR_PLANAR

### Cross-Reference Information

This function calls

    rownorm                            C:\BrainStorm_2001\Toolbox\rownorm.m

This function is called by

    simulator                          C:\BrainStorm_2001\Toolbox\simulator.m

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

    function [R,s] = sensor_axial(R1,baseline);
    %SENSOR_AXIAL - Generate axial gradiometers
    % function [R,s] = sensor_axial(R1,baseline);
    % Given sensor sites in R1, generate
    % axial point gradiometers in radial direction of R1 with baseline
    % separations given in baseline.
    % Each element of the vector baseline should give the total baseline
    % distance from the R1 origin.
    %
    % For example, a BTi 37-channel first-order gradiometer pattern with a
    % 5 cm baseline would by simulated by
    % R1 = sensor_ring(0.12,15*pi/180,4);  % generate sensor sites
    % [R,s] = sensor_axial(R1,[0.05]);
    %
    % A second order gradiometer with a 4 cm baseline would be simulated by
    % [R,s] = sensor_axial(R1,[0.04 0.08]);
    %
    % The first three columns of R and s will be the positions of the coils
    %   nearest the head.  The next three columns correspond to the second coil in
    %   each sensor.
    %
    % See also SENSOR_RING, SENSOR_PLANAR

    %<autobegin> ---------------------- 26-May-2004 11:34:20 -----------------------
    % --------- Automatically Generated Comments Block Using AUTO_COMMENTS ---------
    %
    % CATEGORY: Forward Modeling
    %
    % Alphabetical list of external functions (non-Matlab):
    %   toolbox\rownorm.m
    %
    % At Check-in: $Author: Mosher $  $Revision: 14 $  $Date: 5/26/04 10:02a $
    %
    % 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 11:34:20 -----------------------

    % ----------------------------- Script History ---------------------------------
    % 1994 by John C. Mosher, Ph.D.
    % 19-May-2004 JCM Comments Cleaning
    % ----------------------------- Script History ---------------------------------

    % uses rownorm

    mR = size(R1,1);        % number of sensors
    baseline = baseline(:)';    % make row vector
    baseline = [0 baseline];    % include first coil with offset zero
    nCoils = length(baseline);    % number of coils in each sensor

    sn = rownorm(R1);        % norm of each row of R1
    s1 = R1 ./ sn(:,[1 1 1]);    % radial direction

    % initialize
    R = zeros(mR,nCoils*3); % three columns per coil
    s = R;                % orientations of the coils

    for i = 1:nCoils,
      ndx = (i-1)*3 + [1:3];    % index into columns of R
      R(:,ndx) = R1 + baseline(i)*s1;
      s(:,ndx) = s1;        % orientation remains same
    end

    return

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