void tutest(float data1[], unsigned long n1, float data2[], unsigned long n2,
float *t, float *prob)
{
void avevar(float data[], unsigned long n, float *ave, float *var);
float betai(float a, float b, float x);
float var1,var2,df,ave1,ave2;
avevar(data1,n1,&ave1,&var1);
avevar(data2,n2,&ave2,&var2);
*t=(ave1-ave2)/sqrt(var1/n1+var2/n2);
df=SQR(var1/n1+var2/n2)/(SQR(var1/n1)/(n1-1)+SQR(var2/n2)/(n2-1));
*prob=betai(0.5*df,0.5,df/(df+SQR(*t)));
}
void ttest(float data1[], unsigned long n1, float data2[], unsigned long n2,
float *t, float *prob)
{
void avevar(float data[], unsigned long n, float *ave, float *var);
float betai(float a, float b, float x);
float var1,var2,svar,df,ave1,ave2;
avevar(data1,n1,&ave1,&var1);
avevar(data2,n2,&ave2,&var2);
df=n1+n2-2;
svar=((n1-1)*var1+(n2-1)*var2)/df;
*t=(ave1-ave2)/sqrt(svar*(1.0/n1+1.0/n2));
*prob=betai(0.5*df,0.5,df/(df+(*t)*(*t)));
}
void fasper(float x[], float y[], unsigned long n, float ofac, float hifac,
float wk1[], float wk2[], unsigned long nwk, unsigned long *nout,
unsigned long *jmax, float *prob)
{
void avevar(float data[], unsigned long n, float *ave, float *var);
void realft(float data[], unsigned long n, int isign);
void spread(float y, float yy[], unsigned long n, float x, int m);
unsigned long j,k,ndim,nfreq,nfreqt;
float ave,ck,ckk,cterm,cwt,den,df,effm,expy,fac,fndim,hc2wt;
float hs2wt,hypo,pmax,sterm,swt,var,xdif,xmax,xmin;
*nout=0.5*ofac*hifac*n;
nfreqt=ofac*hifac*n*MACC;
nfreq=64;
while (nfreq < nfreqt) nfreq <<= 1;
ndim=nfreq << 1;
if (ndim > nwk) nrerror("workspaces too small in fasper");
avevar(y,n,&ave,&var);
if (var == 0.0) nrerror("zero variance in fasper");
xmin=x[1];
xmax=xmin;
for (j=2;j<=n;j++) {
if (x[j] < xmin) xmin=x[j];
if (x[j] > xmax) xmax=x[j];
}
xdif=xmax-xmin;
for (j=1;j<=ndim;j++) wk1[j]=wk2[j]=0.0;
fac=ndim/(xdif*ofac);
fndim=ndim;
for (j=1;j<=n;j++) {
ck=(x[j]-xmin)*fac;
MOD(ck,fndim)
ckk=2.0*(ck++);
MOD(ckk,fndim)
++ckk;
spread(y[j]-ave,wk1,ndim,ck,MACC);
spread(1.0,wk2,ndim,ckk,MACC);
}
realft(wk1,ndim,1);
realft(wk2,ndim,1);
df=1.0/(xdif*ofac);
pmax = -1.0;
for (k=3,j=1;j<=(*nout);j++,k+=2) {
hypo=sqrt(wk2[k]*wk2[k]+wk2[k+1]*wk2[k+1]);
hc2wt=0.5*wk2[k]/hypo;
hs2wt=0.5*wk2[k+1]/hypo;
cwt=sqrt(0.5+hc2wt);
swt=SIGN(sqrt(0.5-hc2wt),hs2wt);
den=0.5*n+hc2wt*wk2[k]+hs2wt*wk2[k+1];
cterm=SQR(cwt*wk1[k]+swt*wk1[k+1])/den;
sterm=SQR(cwt*wk1[k+1]-swt*wk1[k])/(n-den);
wk1[j]=j*df;
wk2[j]=(cterm+sterm)/(2.0*var);
if (wk2[j] > pmax) pmax=wk2[(*jmax=j)];
}
expy=exp(-pmax);
effm=2.0*(*nout)/ofac;
*prob=effm*expy;
if (*prob > 0.01) *prob=1.0-pow(1.0-expy,effm);
}
void tptest(float data1[], float data2[], unsigned long n, float *t,
float *prob)
{
void avevar(float data[], unsigned long n, float *ave, float *var);
float betai(float a, float b, float x);
unsigned long j;
float var1,var2,ave1,ave2,sd,df,cov=0.0;
avevar(data1,n,&ave1,&var1);
avevar(data2,n,&ave2,&var2);
for (j=1; j<=n; j++)
cov += (data1[j]-ave1)*(data2[j]-ave2);
cov /= df=n-1;
sd=sqrt((var1+var2-2.0*cov)/n);
*t=(ave1-ave2)/sd;
*prob=betai(0.5*df,0.5,df/(df+(*t)*(*t)));
}
void NR::ftest(Vec_I_DP &data1, Vec_I_DP &data2, DP &f, DP &prob)
{
DP var1,var2,ave1,ave2,df1,df2;
int n1=data1.size();
int n2=data2.size();
avevar(data1,ave1,var1);
avevar(data2,ave2,var2);
if (var1 > var2) {
f=var1/var2;
df1=n1-1;
df2=n2-1;
} else {
f=var2/var1;
df1=n2-1;
df2=n1-1;
}
prob = 2.0*betai(0.5*df2,0.5*df1,df2/(df2+df1*f));
if (prob > 1.0) prob=2.0-prob;
}
void ftest(float data1[], unsigned long n1, float data2[], unsigned long n2,
float *f, float *prob)
{
void avevar(float data[], unsigned long n, float *ave, float *var);
float beta1(float a, float b, float x);
float var1, var2, ave1, ave2, df1, df2;
avevar(data1, n1, &ave1, &var1);
avevar(data2, n2, &ave2, &var2);
if (var1 > var2) {
*f = var1 / var2;
df1 = n1 - 1;
df2 = n2 - 1;
}
else {
*f = var2 / var1;
df1 = n2 - 1;
df2 = n1 - 1;
}
*prob = 2.0*betai(0.5*df2, 0.5*df1, df2 / (df2 + df1*(*f)));
if (*prob > 1.0) *prob = 2.0 - *prob;
}
void period(float x[], float y[], int n, float ofac, float hifac, float px[],
float py[], int np, int *nout, int *jmax, float *prob)
{
void avevar(float data[], unsigned long n, float *ave, float *var);
int i,j;
float ave,c,cc,cwtau,effm,expy,pnow,pymax,s,ss,sumc,sumcy,sums,sumsh,
sumsy,swtau,var,wtau,xave,xdif,xmax,xmin,yy;
double arg,wtemp,*wi,*wpi,*wpr,*wr;
wi=dvector(1,n);
wpi=dvector(1,n);
wpr=dvector(1,n);
wr=dvector(1,n);
*nout=0.5*ofac*hifac*n;
if (*nout > np) nrerror("output arrays too short in period");
avevar(y,n,&ave,&var);
xmax=xmin=x[1];
for (j=1;j<=n;j++) {
if (x[j] > xmax) xmax=x[j];
if (x[j] < xmin) xmin=x[j];
}
xdif=xmax-xmin;
xave=0.5*(xmax+xmin);
pymax=0.0;
pnow=1.0/(xdif*ofac);
for (j=1;j<=n;j++) {
arg=TWOPID*((x[j]-xave)*pnow);
wpr[j] = -2.0*SQR(sin(0.5*arg));
wpi[j]=sin(arg);
wr[j]=cos(arg);
wi[j]=wpi[j];
}
for (i=1;i<=(*nout);i++) {
px[i]=pnow;
sumsh=sumc=0.0;
for (j=1;j<=n;j++) {
c=wr[j];
s=wi[j];
sumsh += s*c;
sumc += (c-s)*(c+s);
}
wtau=0.5*atan2(2.0*sumsh,sumc);
swtau=sin(wtau);
cwtau=cos(wtau);
sums=sumc=sumsy=sumcy=0.0;
for (j=1;j<=n;j++) {
s=wi[j];
c=wr[j];
ss=s*cwtau-c*swtau;
cc=c*cwtau+s*swtau;
sums += ss*ss;
sumc += cc*cc;
yy=y[j]-ave;
sumsy += yy*ss;
sumcy += yy*cc;
wr[j]=((wtemp=wr[j])*wpr[j]-wi[j]*wpi[j])+wr[j];
wi[j]=(wi[j]*wpr[j]+wtemp*wpi[j])+wi[j];
}
py[i]=0.5*(sumcy*sumcy/sumc+sumsy*sumsy/sums)/var;
if (py[i] >= pymax) pymax=py[(*jmax=i)];
pnow += 1.0/(ofac*xdif);
}
expy=exp(-pymax);
effm=2.0*(*nout)/ofac;
*prob=effm*expy;
if (*prob > 0.01) *prob=1.0-pow(1.0-expy,effm);
free_dvector(wr,1,n);
free_dvector(wpr,1,n);
free_dvector(wpi,1,n);
free_dvector(wi,1,n);
}
void period( double x[], double y[], int n, double ofac, double hifac, double px[],
double py[], int np, int *nout, int *jmax, double *prob )
{
// - raèuna Lombov periodogram za nejednoliko razmaknute toèke
// x - niz apscisa u kojima imamo vrijednosti
// y - niz vrijednosti promatrane varijable u danim toèkama apscise
// n - broj toèaka
// ofac - oversampling faktor (tipièno 4 ili više )
// hifac - do koje frekvencije idemo ( do hifac * Nyquistova frekvencija )
// np = ofac * hifac / 2 * N
// px[1..np] - niz frekvencija za koje je izraèunat periodogram
// py[1..np] - vrijednosti periodograma
// jmax - py[jmax] je maksimalni element u py[]
// prob - procjena znaèenja tog maksimuma prema hipotetskom sluèajnm šumu
// ( mala vrijednost indicira da postoji znaèajan periodièki signal)
int i,j;
double ave, c, cc, cwtau, effm, expy, pnow, pymax, s, ss, sumc, sumcy, sums, sumsh,
sumsy, swtau, var, wtau, xave, xdif, xmax, xmin, yy;
double arg, wtemp, *wi, *wpi, *wpr, *wr;
wi = new double[n+1];
wpi = new double[n+1];
wpr = new double[n+1];
wr = new double[n+1];
*nout = (int) (0.5 * ofac * hifac * n);
if( *nout > np )
{
printf("output arrays too short in period ");
assert(0);
}
avevar(y,n, &ave, &var);
xmax = xmin = x[1];
for( j=1; j<=n; j++ )
{
if( x[j] > xmax )
xmax = x[j];
if( x[j] < xmin )
xmin = x[j];
}
xdif = xmax - xmin;
xave = 0.5 * (xmax + xmin);
pymax = 0.0;
pnow = 1.0 / (xdif * ofac);
for( j=1; j<=n; j++ )
{
arg = TWOPID * ((x[j] - xave)*pnow);
wpr[j] = -2.0 * DSQR(sin(0.5*arg));
wpi[j] = sin(arg);
wr[j] = cos(arg);
wi[j] = wpi[j];
}
for( i=1; i<=(*nout); i++ )
{
px[i] = pnow;
sumsh = sumc = 0.0;
for( j=1; j<=n; j++ )
{
c = wr[j];
s = wi[j];
sumsh += s * c;
sumc += (c-s)*(c+s);
}
wtau = 0.5 * atan2(2.0*sumsh, sumc);
swtau = sin(wtau);
cwtau = cos(wtau);
sums = sumc = sumsy = sumcy = 0.0;
for( j=1; j<=n; j++ )
{
s = wi[j];
c = wr[j];
ss = s * cwtau - c * swtau;
cc = c * cwtau + s * swtau;
sums += ss*ss;
sumc += cc*cc;
yy = y[j] - ave;
sumsy += yy*ss;
sumcy += yy*cc;
wr[j] = ((wtemp=wr[j])* wpr[j] - wi[j] * wpi[j]) + wr[j];
wi[j] = (wi[j] * wpr[j] + wtemp * wpi[j]) + wi[j];
}
py[i] = 0.5*(sumcy * sumcy/ sumc + sumsy*sumsy/sums) / var;
if( py[i] >= pymax )
pymax = py[(*jmax=i)];
pnow += 1.0 / (ofac * xdif);
}
expy = exp(-pymax);
effm = 2.0*(*nout) / ofac;
*prob = effm * expy;
if( *prob > 0.01 )
*prob = 1.0-pow(1.0-expy, effm);
delete []wr;
delete []wi;
delete []wpi;
delete []wpr;
}
VImage
PairedTest(VImage *src1, VImage *src2, VImage dest, int n, VShort type) {
int i, j, k, b, r, c, nslices, nrows, ncols;
float ave1, ave2, var1, var2, nx, u;
float sum, smooth = 0;
float t, z, df, sd, cov, *data1 = NULL, *data2 = NULL;
float tiny = 1.0e-10;
nslices = VImageNBands(src1[0]);
nrows = VImageNRows(src1[0]);
ncols = VImageNColumns(src1[0]);
gsl_set_error_handler_off();
dest = VCopyImage(src1[0], NULL, VAllBands);
VFillImage(dest, VAllBands, 0);
VSetAttr(VImageAttrList(dest), "num_images", NULL, VShortRepn, (VShort)n);
VSetAttr(VImageAttrList(dest), "patient", NULL, VStringRepn, "paired_ttest");
if(type == 0)
VSetAttr(VImageAttrList(dest), "modality", NULL, VStringRepn, "tmap");
else
VSetAttr(VImageAttrList(dest), "modality", NULL, VStringRepn, "zmap");
VSetAttr(VImageAttrList(dest), "df", NULL, VShortRepn, (VShort)(n - 1));
/* get smoothness estimates */
sum = nx = 0;
for(i = 0; i < n; i++) {
if(VGetAttr(VImageAttrList(src1[i]), "smoothness", NULL, VFloatRepn, &smooth) == VAttrFound) {
sum += smooth;
nx++;
}
}
for(i = 0; i < n; i++) {
if(VGetAttr(VImageAttrList(src2[i]), "smoothness", NULL, VFloatRepn, &smooth) == VAttrFound) {
sum += smooth;
nx++;
}
}
if(nx > 1) {
VSetAttr(VImageAttrList(dest), "smoothness", NULL, VFloatRepn, sum / nx);
}
data1 = (float *) VMalloc(n * sizeof(float));
data2 = (float *) VMalloc(n * sizeof(float));
df = n - 1;
nx = (float)n;
for(b = 0; b < nslices; b++) {
for(r = 0; r < nrows; r++) {
for(c = 0; c < ncols; c++) {
k = 0;
for(i = 0; i < n; i++) {
data1[i] = VPixel(src1[i], b, r, c, VFloat);
data2[i] = VPixel(src2[i], b, r, c, VFloat);
if(ABS(data1[i]) > tiny && ABS(data2[i]) > tiny)
k++;
}
if(k < n - 3)
continue;
avevar(data1, n, &ave1, &var1);
avevar(data2, n, &ave2, &var2);
if(var1 < tiny || var2 < tiny)
continue;
z = t = 0;
cov = 0;
for(j = 0; j < n; j++)
cov += (data1[j] - ave1) * (data2[j] - ave2);
cov /= df;
u = (var1 + var2 - 2.0 * cov);
if(u < tiny)
continue;
sd = sqrt(u / nx);
if(sd < tiny)
continue;
t = (ave1 - ave2) / sd;
if(isnan(t) || isinf(t))
continue;
switch(type) {
case 0:
VPixel(dest, b, r, c, VFloat) = t;
break;
case 1:
/* z = t2z_approx(t,df); */
z = t2z((double)t, (double)df);
if(t < 0)
z = -z;
VPixel(dest, b, r, c, VFloat) = z;
break;
default:
VError(" illegal type");
}
}
}
}
return dest;
}
void fitexy(float x[], float y[], int ndat, float sigx[], float sigy[],
float *a, float *b, float *siga, float *sigb, float *chi2, float *q)
{
void avevar(float data[], unsigned long n, float *ave, float *var);
float brent(float ax, float bx, float cx,
float (*f)(float), float tol, float *xmin);
float chixy(float bang);
void fit(float x[], float y[], int ndata, float sig[], int mwt,
float *a, float *b, float *siga, float *sigb, float *chi2, float *q);
float gammq(float a, float x);
void mnbrak(float *ax, float *bx, float *cx, float *fa, float *fb,
float *fc, float (*func)(float));
float zbrent(float (*func)(float), float x1, float x2, float tol);
int j;
float swap,amx,amn,varx,vary,ang[7],ch[7],scale,bmn,bmx,d1,d2,r2,
dum1,dum2,dum3,dum4,dum5;
xx=vector(1,ndat);
yy=vector(1,ndat);
sx=vector(1,ndat);
sy=vector(1,ndat);
ww=vector(1,ndat);
avevar(x,ndat,&dum1,&varx);
avevar(y,ndat,&dum1,&vary);
scale=sqrt(varx/vary);
nn=ndat;
for (j=1;j<=ndat;j++) {
xx[j]=x[j];
yy[j]=y[j]*scale;
sx[j]=sigx[j];
sy[j]=sigy[j]*scale;
ww[j]=sqrt(SQR(sx[j])+SQR(sy[j]));
}
fit(xx,yy,nn,ww,1,&dum1,b,&dum2,&dum3,&dum4,&dum5);
offs=ang[1]=0.0;
ang[2]=atan(*b);
ang[4]=0.0;
ang[5]=ang[2];
ang[6]=POTN;
for (j=4;j<=6;j++) ch[j]=chixy(ang[j]);
mnbrak(&ang[1],&ang[2],&ang[3],&ch[1],&ch[2],&ch[3],chixy);
*chi2=brent(ang[1],ang[2],ang[3],chixy,ACC,b);
*chi2=chixy(*b);
*a=aa;
*q=gammq(0.5*(nn-2),*chi2*0.5);
for (r2=0.0,j=1;j<=nn;j++) r2 += ww[j];
r2=1.0/r2;
bmx=BIG;
bmn=BIG;
offs=(*chi2)+1.0;
for (j=1;j<=6;j++) {
if (ch[j] > offs) {
d1=fabs(ang[j]-(*b));
while (d1 >= PI) d1 -= PI;
d2=PI-d1;
if (ang[j] < *b) {
swap=d1;
d1=d2;
d2=swap;
}
if (d1 < bmx) bmx=d1;
if (d2 < bmn) bmn=d2;
}
}
if (bmx < BIG) {
bmx=zbrent(chixy,*b,*b+bmx,ACC)-(*b);
amx=aa-(*a);
bmn=zbrent(chixy,*b,*b-bmn,ACC)-(*b);
amn=aa-(*a);
*sigb=sqrt(0.5*(bmx*bmx+bmn*bmn))/(scale*SQR(cos(*b)));
*siga=sqrt(0.5*(amx*amx+amn*amn)+r2)/scale;
} else (*sigb)=(*siga)=BIG;
*a /= scale;
*b=tan(*b)/scale;
free_vector(ww,1,ndat);
free_vector(sy,1,ndat);
free_vector(sx,1,ndat);
free_vector(yy,1,ndat);
free_vector(xx,1,ndat);
}
void
VROIpaired_ttest(VImage *src1, VImage *src2, VImage *mask, int n, int nmask, FILE *fp) {
VString str;
int i, j, id, b, r, c, c0, c1, nROI = 0;
float ave1 = 0, ave2 = 0, var1 = 0, var2 = 0;
float sum1 = 0, sum2 = 0, u, mx;
float t, z, p, df, sd, cov, *data1 = NULL, *data2 = NULL;
float tiny = 1.0e-8;
float xa, ya, za, xx, yy, zz, voxelsize = 1;
double mean[3];
Volumes *volumes;
Volume vol;
VTrack tc;
VBoolean found = FALSE;
gsl_set_error_handler_off();
/*
** get ROIs from mask
*/
fprintf(stderr, "\n List of ROIs:\n");
fprintf(fp, "\n List of ROIs:\n");
volumes = (Volumes *) VCalloc(nmask, sizeof(Volumes));
nROI = 0;
for(i = 0; i < nmask; i++) {
fprintf(stderr, "\n Mask %2d:\n", i + 1);
fprintf(fp, "\n Mask %2d:\n", i + 1);
volumes[i] = VImage2Volumes(mask[i]);
voxelsize = 1;
if(VGetAttr(VImageAttrList(mask[i]), "voxel", NULL,
VStringRepn, (VPointer) & str) == VAttrFound) {
sscanf(str, "%f %f %f", &xa, &ya, &za);
voxelsize = xa * ya * za;
}
fprintf(stderr, " ROI addr size(mm^3)\n");
fprintf(stderr, "-----------------------------------------------\n");
fprintf(fp, " ROI addr size(mm^3)\n");
fprintf(fp, "-----------------------------------------------\n");
for(vol = volumes[i]->first; vol != NULL; vol = vol->next) {
VolumeCentroid(vol, mean);
if(nROI < vol->label)
nROI = vol->label;
b = mean[0];
r = mean[1];
c = mean[2];
xx = mean[2];
yy = mean[1];
zz = mean[0];
VGetTalCoord(src1[0], zz, yy, xx, &xa, &ya, &za);
id = vol->label;
fprintf(stderr, " %2d %7.2f %7.2f %7.2f %7.0f\n",
id, xa, ya, za, voxelsize *(double)VolumeSize(vol));
fprintf(fp, " %2d %7.2f %7.2f %7.2f %7.0f\n",
id, xa, ya, za, voxelsize *(double)VolumeSize(vol));
}
}
fprintf(stderr, "\n\n");
fprintf(fp, "\n\n");
/* check consistency */
if(nROI < 1)
VError(" no ROIs found");
CheckROI(volumes, nmask, nROI);
/*
** process each ROI
*/
fprintf(stderr, "\n");
fprintf(stderr, " ROI mean t z p \n");
fprintf(stderr, " --------------------------------------------------\n");
if(fp) {
fprintf(fp, "\n");
fprintf(fp, " ROI mean t z p \n");
fprintf(fp, " --------------------------------------------------\n");
}
df = n - 1;
data1 = (float *) VCalloc(n, sizeof(float));
data2 = (float *) VCalloc(n, sizeof(float));
for(id = 1; id <= nROI; id++) {
for(i = 0; i < n; i++) {
j = 0;
if(nmask > 1)
j = i;
found = FALSE;
for(vol = volumes[j]->first; vol != NULL; vol = vol->next) {
if(vol->label != id)
continue;
found = TRUE;
sum1 = sum2 = mx = 0;
for(j = 0; j < VolumeNBuckets(vol); j++) {
for(tc = VFirstTrack(vol, j); VTrackExists(tc); tc = VNextTrack(tc)) {
b = tc->band;
r = tc->row;
c0 = tc->col;
c1 = c0 + tc->length;
for(c = c0; c < c1; c++) {
u = VPixel(src1[i], b, r, c, VFloat);
if(ABS(u) < tiny)
continue;
sum1 += u;
u = VPixel(src2[i], b, r, c, VFloat);
if(ABS(u) < tiny)
continue;
sum2 += u;
mx++;
}
}
}
if(mx < 1) {
VWarning(" no voxels in ROI %d of mask %d", id, i);
data1[i] = data2[i] = 0;
continue;
}
data1[i] = sum1 / mx;
data2[i] = sum2 / mx;
}
if(!found)
goto next;
}
avevar(data1, n, &ave1, &var1);
avevar(data2, n, &ave2, &var2);
if(var1 < tiny || var2 < tiny) {
VWarning(" no variance in ROI %d", id);
continue;
}
z = t = p = 0;
cov = 0;
for(j = 0; j < n; j++)
cov += (data1[j] - ave1) * (data2[j] - ave2);
cov /= df;
sd = sqrt((var1 + var2 - 2.0 * cov) / (df + 1.0));
if(sd < tiny)
continue;
t = (ave1 - ave2) / sd;
if(ABS(t) < tiny)
p = z = 0;
else {
p = t2p((double)t, (double)df);
z = t2z((double)t, (double)df);
if(t < 0)
z = -z;
}
fprintf(stderr, " %3d %8.4f (%.3f) %7.3f %7.3f %7.4f\n",
id, (ave1 - ave2), sd, t, z, p);
if(fp)
fprintf(fp, " %3d %8.4f (%.3f) %7.3f %7.3f %7.4f\n",
id, (ave1 - ave2), sd, t, z, p);
next:
;
}
fprintf(stderr, "\n");
if(fp) {
fprintf(fp, "\n");
fclose(fp);
}
}
double ls_oneperiod(double *x, double *y, int n, double period)
{
/* This routine is based on the "period" function in Numerical Recipes in C by Press et al., it skips the loop over periods though */
void avevar(double *data, int n, double *ave, double *var);
int j;
double ave, c, cc, cwtau, pnow, pymax, s, ss, sumc, sumcy, sums, sumsh, sumsy, swtau, var, wtau, xave, xdif, xmax, xmin, yy;
double arg, *wi, *wpi, *wpr, *wr;
wi = (double *) malloc(n*sizeof(double));
wpi = (double *) malloc(n * sizeof(double));
wpr = (double *) malloc(n * sizeof(double));
wr = (double *) malloc(n * sizeof(double));
avevar(y,n,&ave,&var);
xmax = xmin=x[0];
for (j=0;j<n;j++) {
if(x[j] > xmax) xmax = x[j];
if(x[j] < xmin) xmin = x[j];
}
xdif = xmax - xmin;
xave = 0.5*(xmax + xmin);
pymax = 0.0;
pnow = 1.0/(period);
for (j=0;j<n;j++) {
arg = TWOPID*((x[j]-xave)*pnow);
wpr[j] = -2.0*SQR(sin(0.5*arg));
wpi[j] = sin(arg);
wr[j] = cos(arg);
wi[j] = wpi[j];
}
pnow = 1./period;
sumsh = sumc = 0.0;
for(j=0;j<n;j++) {
c = wr[j];
s = wi[j];
sumsh += s*c;
sumc += (c-s)*(c+s);
}
wtau = 0.5*atan2(2.0*sumsh,sumc);
swtau = sin(wtau);
cwtau = cos(wtau);
sums=sumc=sumsy=sumcy=0.0;
for(j=0;j<n;j++) {
s = wi[j];
c = wr[j];
ss = s*cwtau-c*swtau;
cc = c*cwtau+s*swtau;
sums += ss*ss;
sumc += cc*cc;
yy = y[j] - ave;
sumsy += yy*ss;
sumcy += yy*cc;
}
pymax=0.5*(sumcy*sumcy/sumc+sumsy*sumsy/sums)/var;
free(wi);
free(wpi);
free(wpr);
free(wr);
return pymax;
}
