Dear Rene,
I've tried to use TGraph::LeastSquareFit() without success, probably I am
doing something wrong. Here is the script and output. I tried ROOT versions
3.03/2 and 3.02/7 with the same result.
Thank you, Yuriy.
------------------------------------------- Script -----------------------
TCanvas *c;
TGraph *g, gg;
Double_t par[20];
void pfit() {
c = new TCanvas( "c1", "c1" );
Double_t *px = new Double_t[10000];
Double_t *py = new Double_t[10000];
Int_t i;
Double_t x;
Double_t dx = 0.01;
for( x=-5, i=0; i<1000; i++, x+=dx ) {
px[i] = x; py[i] = x*x+2*x-1;
}
g = new TGraph( i, px, py );
g->Draw("AP");
g->LeastSquareFit( i, 3, par );
printf( "%f\n", par[0] );
printf( "%f\n", par[1] );
printf( "%f\n", par[2] );
delete px;
delete py;
}
------------------------------------------- Output -----------------------
14.000000
0.000000
0.000000
while I expect 1, 2, -1.
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