Dear all,
I seem to be missing some vital step in using a user defined equation to fit to a histogram.
I am trying to use the function gks from the script gks.C (that Rene produced for me yesterday) as a fitting function for the Monte Carlo data that we produce from a FORTRAN program. I have attached a copy of a root file containing a typical set of such data (file MCGcalc.root).
I have compiled Rene's script (using the command ".x gks.C+") and produced a shared object gks_C.so.
I have loaded gks_C.so (using the command ".L gks_C.so") and then tried to fit using various permutations of commands such as
G2values.Fit("gks")
but everything I have tried so far gives rise to messages similar to "Unknown function: gks" (with the occasional seg fault).
I have been similarly unsuccessful using the FitPanel GUI.
Any guidance you can give on what I might be doing wrong would be greatly appreciated.
Regards
Russell Leslie
Nuclear Physics
R.S.Phys.S.E.
ANU
>
>
> ---------- Forwarded message ----------
> From: Rene Brun <Rene.Brun_at_cern.ch>
> Date: Thu, Feb 19, 2009 at 7:16 PM
> Subject: Re: [ROOT] Seeking guidance on implementing a user defined equation in ROOT
> To: Russell Leslie <u4504546_at_anu.edu.au>
> Cc: roottalk_at_lxbuild091.cern.ch
>
>
> Try the function gks.C in attachment
> To run do:
> root > .x gks.C+
>
> Rene Brun
>
> Russell Leslie wrote:
> Dear all,
> NOTE - message resent because I sent this originally from another account and it did not turn up on the roottalk list.
> I am still feeling my way forward on ROOT, but I have found it to be a very useful tool-set.
> One problem I am currently working on is to try to implement the following equations in ROOT (LaTex form of the equations below).
>
> $$
> G_{k}(t) = e^{-\Lambda^{*} t}G_{k}^{(fluct.)}(t)+ \int_{0}^{t} \Lambda^{*} G_{k}^{(fluct.)}(t')\cdotp e^{-\Lambda^{*} t'}G_{k}^{(stat.)} (t-t')dt'
> $$
> Where Gk(stat) is give by the following equation
> $$
> G_{k}^{(stat.)} (t) = \left\langle \alpha_{k} \right\rangle + ( 1 - \left\langle \alpha_{k}\right\rangle )e^{- \Gamma t}
> $$
> and Gk(fluct) is given by the this equation
> $$
> G_{k}^{(fluct.)}(t) = ( 1 - \lambda_{k}\tau_{c} )e^{ - \lambda _{k} t }
> $$
> The equations are from the manual for the Coulex code GOSIA and I want to use them as the fitting function for the output of a Monte Carlo simulation that we use.
> I have had no problems producing the curves for Gk(stat) and Gk(fluct) - but I have not been able to implement the integral term in the Gk equation (the first equation above). The code I have so far is given below
> {
> //Calculate Gks
> //parameter[0] = alpha_k
> //parameter[1] = gamma
> TF1 *Gks = new TF1("Gks","[0]+(1-[0])*exp(-[1]*x)",0,15);
> Gks->SetParameters(0.221243,0.4);
> //Calculate Gkf
> //parameter[0] = lambda_k
> //parameter[1] = tau_c
> TF1 *Gkf = new TF1("Gkf","(1-[0]*[1])*exp(-[0]*x)",0,15);
> Gkf->SetParameters(0.172,0.5);
> //Calculate expLamba*t
> //parameter[0] = 1 //parameter[1] = Lambda*
> TF1 *eLst = new TF1("eLst","[0]*exp(-[1]*x)",0,15);
> eLst->SetParameters(1,0.0345);
> //Combine Gks and Gkf to for Gkcalc
> TF1 *Gkcalc = new TF1("Gkcalc","Gkf*eLst*[0]*[1]",0,15); // This is the bit I can't get!!!!!!!!
> //Create a canvas to draw Gkcalc
> TCanvas *Gkcalc1 = new TCanvas("Gkcalc1","Gkcalc1",10,10,1400,1200);
> //Draw and format Gkcalc
> Gkcalc->Draw();
> Gkcalc->SetLineWidth(2.0);
> Gkcalc->SetLineColor(kBlue);
> Gkcalc->GetXaxis()->SetTitle("time");
> Gkcalc->GetYaxis()->SetTitle("G_{k}(t)");
> Gkcalc->SetTitle("G_{k}(t) = e^{-#Lambda^{*} t}G_{k}^{(fluct.)}(t)+ #int_{0}^{t} #Lambda^{*} G_{k}^{(fluct.)}(t').e^{-#Lambda^{*} t'}G_{k}^{(stat.)} (t-t')dt' ");
> Gkcalc->GetYaxis()->SetLabelFont(22);
> Gkcalc->GetYaxis()->SetTitleFont(22);
> Gkcalc->GetXaxis()->SetLabelFont(22);
> Gkcalc->GetXaxis()->SetTitleFont(22);
> //Add other lines
> Gks->Draw("same");
> Gks->SetLineWidth(2.0);
> Gks->SetLineColor(kRed);
> Gkf->Draw("same");
> Gkf->SetLineWidth(2.0);
> Gkf->SetLineColor(kGreen);
> eLst->Draw("same");
> eLst->SetLineWidth(2.0);
> eLst->SetLineColor(kMagenta);
> TLegend *legend = new TLegend(.75,.80,.95,.95);
> legend->AddEntry(Gkcalc,"G_{k}(t)");
> legend->AddEntry(Gks,"G_{k}^{(stat)}(t)");
> legend->AddEntry(Gkf,"G_{k}^{(fluct)}(t)");
> legend->AddEntry(Gks,"e^{-#Lambda^{*} t}");
> legend->Draw();
> }
> My root details as as follows ROOT 5.18/00b (branches/v5-18-00-patches_at_22563 <mailto:branches/v5-18-00-patches_at_22563>, Oct 19 2008, 22:04:00 on linuxx8664gcc4.3)
> Any help or guidance you can give on this would be greatly appreciated.
> Russell Leslie
> Nuclear Physics
> R.S.Phys.S.E.
> ANU
>
>
NOTE - retransmission because I seem to have done something wrong the first time I sent this.
Russell Leslie
Nuclear Physics
R.S.Phys.S.E.
ANU
Received on Fri Feb 20 2009 - 11:12:04 CET
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