SetParLimits bug

From: Matt Fritts (mcfritts@accesstoledo.com)
Date: Wed Jul 28 1999 - 19:29:43 MEST


I've been having a minor problem with a fitting macro I've been writing. I
wanted to include an option to set a constant to zero, but it's not
working. I can illustrate the problem with this test macro:


{
Float_t exconst;

Float_t x[5], y[5], xe[5], ye[5];
for(int l=0;l<5;l++){
 x[l]=l;
 y[l]=11*pow(l,2)-330*l+2500;
 xe[l]=.2;
 ye[l]=2.5;
}

//  define fit function  //
TF1 *e1 = new TF1("e1","[0]*x+[1]",.5,15);

//  set guess parameters  //
e1.SetParameter(0,2000);
e1.SetParameter(1,1);

printf("Enter constant: ");
scanf("%f",&exconst);
e1.SetParLimits(1,exconst,exconst);
e1.SetParameter(1,exconst);

gre = new TGraphErrors(5,x,y,xe,ye);
gre.Fit("e1");
}


The macro will fix parameter 1 properly for any entered value except zero.
If zero is entered, it fits parameter 1. (At least in Root Version 2.21/08.)

By the way, thanks for the help with the download.

-Matt Fritts



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