Hello,
I do not quite understand how the function TF1::FixParameter works. When I run the following macro,
{
TH1* Hist = new TH1I( "Hist", "Hist", 21, -10.5, +10.5 ); Hist->FillRandom( "gaus" );
TF1* Fit = new TF1( "myfit", "gaus" ); Fit->FixParameter( 1, 0.0 );
Hist->Fit( Fit );
}
where I fit a random gaussian distribiution with a function whose mean I fixed at 0.0, I get e.g. the following result:
FCN=3.83732 FROM MIGRAD STATUS=CONVERGED 41 CALLS 42 TOTAL
EDM=1.02145e-10 STRATEGY= 1 ERROR MATRIX ACCURATE EXT PARAMETER STEP FIRST NO. NAME VALUE ERROR SIZE DERIVATIVE 1 Constant 2.00922e+03 3.46544e+01 3.05267e-02 -2.58214e-07 2 Mean -9.80000e-03 fixed 3 Sigma 9.92018e-01 9.78696e-03 2.89142e-06 -5.29594e-03
Ok, the mean is close to 0.0 and declared 'fixed', but why is it not exactly 0.0?
Thanks for any clarifications
Thomas
-- Thomas Lauf MPE - MPI Halbleiterlabor E-Mail: thl_at_hll.mpg.deReceived on Mon Dec 17 2007 - 11:39:38 CET
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