Hi, The follwing macro fails to calculate y = expExp->EvalPar(x,a); At the prompt I type .L expExp.C .x cjj_g10.C All values printed to screen for y are 0. Everything is printed correctly. Any ideas? Also, is it possible to subtract a function from a histgram to get the residuals of a fit, say. This feature would be very nice if it is not currently in place. I am running 1.03/09 on a linux box. Thanks, Chris The complete macro follows { gROOT->Reset(); gStyle->SetOptFit(1); gStyle->SetStatX(0.45); gStyle->SetStatY(0.85); TCanvas* c1 = new TCanvas("c1","Ntuple Plots",1); // create canvas c1->SetFillColor(kWhite); TFile* f1 = new TFile("cjj_g10.root","READ"); TH1F* hi1 = new TH1F("hi1","Angular Resolution: Gamma Energy = 10 MeV ",80,-1.0,1.0); hi1->SetXTitle("Cos`q#"); // h509->Draw("Angres>>hi1","Egen>4&&Rfitt<600","goff"); h503->Draw("(Ue*Uf+Ve*Vf+We*Wf)>>hi1","Rfit<600","goff"); c1->SetLogy(1); TF1* expExp = new TF1("expExp",expExp,-1,1,4); expExp->SetParameters(9.2,0.2,5.7,17000); expExp->SetParNames("1st slope","2nd Amp","2nd slope","scale fac"); Double_t x[1]; Double_t a[4]; a[0] = 9.2; a[1] = 0.2; a[2] = 5.7; a[3] = 17000.0; Double_t y; printf("Hello\n"); for( Int_t i=0 ; i<80 ; i++) { x[0] = -0.9875+i*0.025; y = expExp->EvalPar(x,a); printf("%d\t%f\t%f\t%f\n",i,hi1->GetBinContent(i),x[0],y); } expExp->Draw(); /* expExp->SetParLimits(0,9.2,9.3); expExp->SetParLimits(1,0.2,0.21); expExp->SetParLimits(2,5.7,5.8); expExp->SetParLimits(3,17000.0,17100.0); TPostScript ps("cjj_g10.eps",114); hi1->Fit("expExp","RB"); // expExp->Draw(); // hi1->Draw("same"); c1->Update(); ps.Close(); */ } The function expExp is ... Double_t expExp(Double_t* x, Double_t* par) { Double_t expPart1 = exp(par[0]*(x[0]-1)); Double_t expPart2 = exp(par[2]*(x[0]-1)); return (par[3]* (expPart1 + par[1]*expPart2)); } ================================================================= = = = Chris Jillings = = Department of Physics phone/voice mail: (613) 545-6000x4805 = = Queen's University fax: (613) 545-6813 = = Kingston, Ontario email: chris@sno.phy.queensu.ca = = Canada, K7L 3N6 web: http://snodaq.phy.queensu.ca = = = =================================================================
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