Re: Can't fix sigma in gaus ...

Hi Arthur,

See <http://root.cern.ch/root/html/TH1#TH1:Fit@1> for the fit option "B".

Cheers, Axel.

On 06/27/2012 12:41 AM, Arthur E. Snyder wrote:
> I find I can't fix |sigma| in function 'gaus'
>
> root [3] fgau->FixParameter(2,1)
> root [4] fgau->Print()
> gaus : gaus Ndim= 1, Npar= 3, Noper= 1
> fExpr[0] = gaus action = 110 action param = 0
> Optimized expression
> fExpr[0] = gaus action = 110 action param = 0
> Par 0 Constant = 1
> Par 1 Mean = 0
> Par 2 Sigma = 1
> root [5] hSignif->Draw()
> root [6] hSignif->SetAxisRange(-4,4)
> root [7] hSignif->Fit(fgau)
> FCN=43.6279 FROM MIGRAD STATUS=CONVERGED 68 CALLS 69
> TOTAL
> EDM=4.24208e-13 STRATEGY= 1 ERROR MATRIX
> UNCERTAINTY 2.2 per cent
> EXT PARAMETER STEP FIRST
> NO. NAME VALUE ERROR SIZE DERIVATIVE
> 1 Constant 5.51347e+00 6.30205e-01 8.36689e-05 -2.02569e-06
> 2 Mean -1.13119e-01 1.17954e-01 -8.33876e-06 6.14754e-06
> 3 Sigma 1.23109e+00 1.39661e-01 -2.78385e-06 -1.57846e-05
> (class TFitResultPtr)174529088
>
> --FixParameter works for |Constant| and |mean|
>
> --That does not seem right! A bug? Hard to believe it would not have
> noticed previouly though --
>
> ????
>
> -AE
>
>
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Received on Wed Jun 27 2012 - 09:17:59 CEST