Re: Limiting Y range in TGraph::Fit

From: OKUMURA, Akira <oxon_at_astro.isas.jaxa.jp>
Date: Tue, 19 Oct 2010 12:13:32 -0700

Hello Rene,

Thank you for your quick reply. But it does not work as I expected. In the following example, the fit result should be y = x, by the actual result is y = 1.4 x - 0.8

root [0] TGraph* gra = new TGraph
root [1] gra->SetPoint(0, 0, -1)
root [2] gra->SetPoint(1, 1, 1)
root [3] gra->SetPoint(2, 2, 2)
root [4] gra->SetPoint(3, 3, 3)
root [5] gra->SetPoint(4, 4, 5)
root [6] gra->SetMaximum(4)
root [7] gra->SetMinimum(0)
root [8] gra->Fit("pol1")                                                       
****************************************
Minimizer is Linear
Chi2                      =          0.4
NDf                       =            3
p0                        =         -0.8   +/-   0.282843    
p1                        =          1.4   +/-   0.11547     

(class TFitResultPtr)4329991824
root [9] gra->Draw("a*")

Regards,

--
OKUMURA, Akira oxon@{astro.isas.jaxa.jp,stanford.edu}
Institute of Space and Astronautical Science (ISAS/JAXA)
Now at KIPAC/SLAC/Stanford
Varian Physics #306, 382 Via Pueblo Mall, MC 4060
Stanford, CA 94305-4060
TEL 650-736-0971/FAX 650-724-5065
Skype : okumura.akira

On 2010/10/19, at 11:53, Rene Brun wrote:

> Use TGraph::SetMaximum, SetMinimum
> 
> Rene Brun
> 
> 
> On 19/10/2010 20:45, OKUMURA, Akira wrote:


>> Hello ROOTers,

>> 

>> Is there any simple way to limit the Y range in TGraph::Fit?

>> 

>> The 4th and 5th arguments (rxmin, rxmax) in the regular TGraph::Fit method are used for the high/low limit of the X axis. But I would like to set rymin and rymax instead.

>> 

>> Of course, I can do it manually by removing data points outside the range from a graph. But if there is a better solution which is already implemented, I would use it.

>> 

>> Regards,

>> 

>> --

>> OKUMURA, Akira oxon@{astro.isas.jaxa.jp,stanford.edu}

>> Institute of Space and Astronautical Science (ISAS/JAXA)

>> Now at KIPAC/SLAC/Stanford

>> Varian Physics #306, 382 Via Pueblo Mall, MC 4060

>> Stanford, CA 94305-4060

>> TEL 650-736-0971/FAX 650-724-5065

>> Skype : okumura.akira

>> 

> 

Received on Tue Oct 19 2010 - 21:13:46 CEST