65 lines
1.0 KiB
C++
65 lines
1.0 KiB
C++
#include <cmath>
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#include "nr.h"
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using namespace std;
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DP aa,abdevt;
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const Vec_DP *xt_p,*yt_p;
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void NR::medfit(Vec_I_DP &x, Vec_I_DP &y, DP &a, DP &b, DP &abdev)
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{
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int j;
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DP bb,b1,b2,del,f,f1,f2,sigb,temp;
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DP sx=0.0,sy=0.0,sxy=0.0,sxx=0.0,chisq=0.0;
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int ndata=x.size();
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xt_p= &x;
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yt_p= &y;
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for (j=0;j<ndata;j++) {
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sx += x[j];
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sy += y[j];
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sxy += x[j]*y[j];
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sxx += x[j]*x[j];
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}
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del=ndata*sxx-sx*sx;
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aa=(sxx*sy-sx*sxy)/del;
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bb=(ndata*sxy-sx*sy)/del;
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for (j=0;j<ndata;j++)
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chisq += (temp=y[j]-(aa+bb*x[j]),temp*temp);
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sigb=sqrt(chisq/del);
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b1=bb;
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f1=rofunc(b1);
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if (sigb > 0.0) {
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b2=bb+SIGN(3.0*sigb,f1);
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f2=rofunc(b2);
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if (b2 == b1) {
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a=aa;
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b=bb;
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abdev=abdevt/ndata;
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return;
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}
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while (f1*f2 > 0.0) {
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bb=b2+1.6*(b2-b1);
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b1=b2;
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f1=f2;
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b2=bb;
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f2=rofunc(b2);
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}
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sigb=0.01*sigb;
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while (fabs(b2-b1) > sigb) {
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bb=b1+0.5*(b2-b1);
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if (bb == b1 || bb == b2) break;
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f=rofunc(bb);
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if (f*f1 >= 0.0) {
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f1=f;
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b1=bb;
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} else {
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f2=f;
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b2=bb;
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}
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}
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}
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a=aa;
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b=bb;
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abdev=abdevt/ndata;
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}
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