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go_leadfield.c
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go_leadfield.c
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#include <string.h>
#include <math.h>
#include "mex.h"
#include "matrix.h"
void
mexFunction (int nlhs, mxArray * plhs[], int nrhs, const mxArray * prhs[])
{
mxArray *lf;
double nr, na, dar, F, tmp2;
double a[3], tmp1[3], delF[3], B[3], cqr[3], um[3], rm[3];
double *lf_p, *rm_p, *um_p, *R, *Q;
char str[256];
if (nrhs<4)
mexErrMsgTxt("Not enough input arguments");
if (nrhs>4)
mexErrMsgTxt("Too many input arguments");
if (mxGetM(prhs[0])!=1 || mxGetN(prhs[0])!=3)
mexErrMsgTxt ("Invalid dimension for input argument 1");
if (mxGetN(prhs[1])!=3)
mexErrMsgTxt ("Invalid dimension for input argument 2");
if (mxGetN(prhs[2])!=3)
mexErrMsgTxt ("Invalid dimension for input argument 3");
if (mxGetN(prhs[3])!=3)
mexErrMsgTxt ("Invalid dimension for input argument 4");
lf = mxCreateDoubleMatrix(1, 1, mxREAL);
lf_p = mxGetData(lf);
R = mxGetData(prhs[0]);
Q = mxGetData(prhs[1]);
rm_p = mxGetData(prhs[2]);
um_p = mxGetData(prhs[3]);
/* unpack the pointers (in the faintest hope this works) */
rm[0] = rm_p[0];
rm[1] = rm_p[1];
rm[2] = rm_p[2];
um[0] = um_p[0];
um[1] = um_p[1];
um[2] = um_p[2];
/* compute the difference between this channel and the dipole position */
a[0] = rm[0] - R[0];
a[1] = rm[1] - R[1];
a[2] = rm[2] - R[2];
nr = sqrt(rm[0]*rm[0] + rm[1]*rm[1] + rm[2]*rm[2]); /* norm(rm) */
na = sqrt(a[0]*a[0] + a[1]*a[1] + a[2]*a[2]); /* norm(a) */
tmp1[0] = a[0] / na;
tmp1[1] = a[1] / na; /* a/norm(a) */
tmp1[2] = a[2] / na;
dar = tmp1[0]*R[0] + tmp1[1]*R[1] + tmp1[2]*R[2]; /* dot(tmp1,R) */
cqr[0] = Q[1]*R[2] - Q[2]*R[1];
cqr[1] = Q[2]*R[0] - Q[0]*R[2]; /* cross(Q,R) */
cqr[2] = Q[0]*R[1] - Q[1]*R[0];
F = na*(nr*na + nr*nr - (R[0]*rm[0] + R[1]*rm[1] + R[2]*rm[2]));
delF[0] = ((na*na)/nr + dar + 2*na + 2*nr)*rm[0] - (na + 2*nr + dar)*R[0];
delF[1] = ((na*na)/nr + dar + 2*na + 2*nr)*rm[1] - (na + 2*nr + dar)*R[1];
delF[2] = ((na*na)/nr + dar + 2*na + 2*nr)*rm[2] - (na + 2*nr + dar)*R[2];
tmp2 = cqr[0]*rm[0] + cqr[1]*rm[1] + cqr[2]*rm[2]; /* dot( cqr , rm) */
B[0] = (F*cqr[0]-tmp2*delF[0])*1e-7/(F*F);
B[1] = (F*cqr[1]-tmp2*delF[1])*1e-7/(F*F);
B[2] = (F*cqr[2]-tmp2*delF[2])*1e-7/(F*F);
lf_p[0] = B[0]*um[0] + B[1]*um[1] + B[2]*um[2];
plhs[0] = lf;
return;
}