Can't fix sigma in gaus ...

From: Arthur E. Snyder <snyder_at_slac.stanford.edu>
Date: Tue, 26 Jun 2012 15:41:47 -0700


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

A.E. Snyder, The Former Group C (TFC)        \!c*p?/
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Received on Wed Jun 27 2012 - 00:41:55 CEST

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