Hi,
- I have a root-tuple containing various TGraphErrors graphs.
- The existing TGraphErrors have their points joined with straight lines.
- I want to fit these graphs with exponentials.
- I want to display the fitted curves and the points with error bars, but
NOT the straight lines joining the points.
- I also need to superimpose more than one fitted graph on the same axis,
and add a legend too.
I tried fitting a graph in 2 ways:
1. I drew the graph by clicking in the TBrowser, then fitted it. However,
the straight lines remain on the graph.
root [0] TCanvas *c1 = new TCanvas
root [1] TBrowser QQ
(I drew the graph using the TBrowser)
root [2] TF1 *E1 = new TF1("E1","[0] + [1]*exp(-[2]*x)",20,86)
root [3] Graph_calparton_c->Fit("E1","R")
**********
** 1 **SET ERR 1
**********
**********
** 5 **MIGRAD 5000 3.533e-11
**********
MIGRAD MINIMIZATION HAS CONVERGED.
FCN=0.923423 FROM MIGRAD STATUS=CONVERGED 266 CALLS 267
TOTAL
EDM=1.71871e-19 STRATEGY= 1 ERROR MATRIX
UNCERTAINTY
1.8 per cent
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 p0 9.04319e-02 5.72987e-03 7.28854e-10 1.39468e-08
2 p1 1.37449e-01 1.23834e-02 1.12821e-09 -1.06242e-07
3 p2 3.63376e-02 6.92076e-03 9.83969e-10 1.49311e-07
FCN=0.923423 FROM MIGRAD STATUS=CONVERGED 266 CALLS 267
TOTAL
EDM=1.71871e-19 STRATEGY= 1 ERROR MATRIX
UNCERTAINTY
1.8 per cent
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 p0 9.04319e-02 5.72987e-03 7.28854e-10 1.39468e-08
2 p1 1.37449e-01 1.23834e-02 1.12821e-09 -1.06242e-07
3 p2 3.63376e-02 6.92076e-03 9.83969e-10 1.49311e-07
(Int_t)0
root [4] E1->Draw("same")
-----
2. I created some axes and drew the graph onto them. When I try to fit
ROOT crashes:
root [0] TBrowser B
root [1] TCanvas *c1 = new TCanvas
root [2] htemp = new TH2F("htemp","title",100,17,92,100,0.08,0.19)
(class TH2F*)0x108da310
root [3] htemp->Draw()
root [4] TFile *f1 = new TFile("NEWzhall_5.root")
root [5] Graph_calparton_c->Draw()
root [6] TF1 *E1 = new TF1("E1","[0] + [1]*exp(-[2]*x)",20,86)
root [7] Graph_calparton_c->Fit("E1","R")
**********
** 1 **SET ERR 1
**********
**********
** 5 **MIGRAD 5000 3.533e-11
**********
MIGRAD MINIMIZATION HAS CONVERGED.
FCN=0.923423 FROM MIGRAD STATUS=CONVERGED 266 CALLS 267
TOTAL
EDM=1.71871e-19 STRATEGY= 1 ERROR MATRIX
UNCERTAINTY 1.8 per cent
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 p0 9.04319e-02 5.72987e-03 7.28854e-10 1.39468e-08
2 p1 1.37449e-01 1.23834e-02 1.12821e-09 -1.06242e-07
3 p2 3.63376e-02 6.92076e-03 9.83969e-10 1.49311e-07
FCN=0.923423 FROM MIGRAD STATUS=CONVERGED 266 CALLS 267
TOTAL
EDM=1.71871e-19 STRATEGY= 1 ERROR MATRIX
UNCERTAINTY 1.8 per cent
EXT PARAMETER STEP FIRST
NO. NAME VALUE ERROR SIZE DERIVATIVE
1 p0 9.04319e-02 5.72987e-03 7.28854e-10 1.39468e-08
2 p1 1.37449e-01 1.23834e-02 1.12821e-09 -1.06242e-07
3 p2 3.63376e-02 6.92076e-03 9.83969e-10 1.49311e-07
(Int_t)0
*** Break *** segmentation violation
Root >
*** Break *** segmentation violation
Root >
*** Break *** segmentation violation
Root >
-----
a) How do I fit a TGraph / TGraphErrors without displaying the straight
lines?
b) I need to create axes on which to superimpose several different graphs.
How can I fit each graph and superimpose them?
Thanks very much for your help,
Amber
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