Overalying histograms

ROOT
1

Hi,

I am trying to overlay two histograms both with a line of best fit. I can overlay them by using psame with no fits and when I only put the fit on one of the histograms. However when I put the fit on the second histogram it does not plot that histogram at all.

Is there a ‘knack’ that Im not doing to make both histograms and fits appear on the same canvas? Im using the root script below plus attached plot where histo1 is in blue and histo2 in pink.
Thanks
histo1->Fit(“pol1”);
histo1->Draw(“P”);
//histo2->Fit(“pol1”); // uncommenting this = histo2 does not plot at all
histo2->Draw(“psame”);

plot1.gif1134×728 40.4 KB

2

Instead of

histo1->Fit("pol1"); histo1->Draw("P"); //histo2->Fit("pol1"); // uncommenting this = histo2 does not plot at all histo2->Draw("psame"); do

histo1->Fit("pol1","","p"); histo2->Fit("pol1","',"psame");
see doc of TH1::Fit

Rene

3

Great this works.
Thanks a lot for your help.