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root:pyroot_th1 [2017/06/22 12:09] – [Filling a histogram from a tree] iwnroot:pyroot_th1 [2017/09/05 10:35] (current) – [Handling TH1 histograms] iwn
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 +[[root:root|Getting started with ROOT]] -> [[root:pyroot|Useful pyROOT snippets]] → [[root:pyroot_th1|Handling TH1 histograms]]
 +
 ====== Handling TH1 histograms ====== ====== Handling TH1 histograms ======
  
-To use ''TH1D'' in ''python'', you can either do+[[https://root.cern.ch/doc/master/classTH1.html|Here]] is the class reference for ''TH1''. 
 + 
 + 
 +===== Importing ROOT classes ===== 
 + 
 +To use ''TH1D'' in ''python'', you can either only import a ''TH1D'' class:
 <code python> <code python>
 from ROOT import TH1D from ROOT import TH1D
 hist = TH1D("hist_name","hist_title",100,0,100) hist = TH1D("hist_name","hist_title",100,0,100)
 </code> </code>
-or+or //all// classes:
 <code python> <code python>
 from ROOT import * # loads all classes, and thus takes longer from ROOT import * # loads all classes, and thus takes longer
 hist = TH1D("hist_name","hist_title",100,0,100) hist = TH1D("hist_name","hist_title",100,0,100)
 </code> </code>
-or+or only the ''ROOT'' module:
 <code python> <code python>
 import ROOT import ROOT
Line 54: Line 61:
 tree.Draw("abs(eta) >> hist_name") tree.Draw("abs(eta) >> hist_name")
 tree.Draw("pt1*(eta1<2.4) + pt2*(eta2<2.4) >> hist_name") # boolean expressions tree.Draw("pt1*(eta1<2.4) + pt2*(eta2<2.4) >> hist_name") # boolean expressions
 +</code>
 +This also includes custom functions, which you can load into ''ROOT'' with a ''C'' file:
 +<code python>
 +from ROOT import gROOT, ...
 +gROOT.Macro("myfunctions.C+")
 +...
 +tree.Draw("deltaR(eta1,phi1,eta2,phi2) >> hist_name")    # deltaR     function defined in "myfunctions.C+"
 +tree.Draw("pt1 >> hist_name","(pt>30)*weightEta1(eta1)") # weightEta1 function defined in "myfunctions.C+"
 </code> </code>
  
Line 75: Line 90:
 </code> </code>
  
-It's also possible to pass some option you would normally use in "TH1::Draw()". It is passed as the third string.+It's also possible to pass some **draw option** you would normally use in "TH1::Draw()". It is passed as the third string.
 <code python> <code python>
 tree.Draw("px >> h1(100,0,100)","","E2") tree.Draw("px >> h1(100,0,100)","","E2")
Line 90: Line 105:
 [2] tree->Draw("px >> h1(100,0,100)","pt>20") [2] tree->Draw("px >> h1(100,0,100)","pt>20")
 [3] tree->Draw("px >> h1(100,0,100)","","E2") [3] tree->Draw("px >> h1(100,0,100)","","E2")
-[4] tree->Draw("py >> h2(100,0,100)","","E2 SAME")+[4] tree->Draw("py >> h2(100,0,100)","","E2 SAME") // compare to px
 </code> </code>
root/pyroot_th1.1498126147.txt.gz · Last modified: 2017/06/22 12:09 by iwn

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