Hi, the function FitSlicesY has simplied quite some coding for me. But I have problem updating the resulting histograms. Here is what I did: root [1] TTree *TLQ=(TTree*)LQ->Get("h10"); root [2] TH2F *energy=new TH2F("energy","",25,0,500,160,-1,1); root [3] TLQ->Draw("(pe[3]-epe[0])/epe[0]:pe[3]>>energy","Ejetc[0]>100"); Warning in <MakeDefCanvas>: creating a default canvas with name c1 root [5] energy->FitSlicesY() root [6] energy_1->Draw() //draw the mean of each slices so far everything is fine. Now I want to remove the cut when projecting into the histogram. Simply do: TLQ->Draw("(pe[3]-epe[0])/epe[0]:pe[3]>>energy",""); energy->FitSlicesY() energy_1->Draw() and I obtained the identical energy_1 as before, ie, I did not get root to be awrare of the updated energy_1. Then I tried to delete all the histograms in the following order: delete energy delete energy_0 delete energy_1 delete energy_2 delete energy_chi2 and I try to make the new histogram again: TLQ->Draw("(pe[3]-epe[0])/epe[0]:pe[3]>>energy",""); energy->FitSlicesY() energy_1->Draw() Error: No symbol energy_1->Draw() in current scope FILE:/var/tmp/zaaa030JK LINE:1 If, when deleting all the energy's histograms, I delete energy in the last: delete energy_0 delete energy_1 delete energy_2 delete energy_chi2 delete energy and then try to make the new histogram again: TLQ->Draw("(pe[3]-epe[0])/epe[0]:pe[3]>>energy",""); energy->FitSlicesY() energy_1->Draw() *** Break *** segmentation violation May I know what I missed? Best regards, Wuyi
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