Differences

This shows you the differences between two versions of the page.

--- hepsim:jas4pp [2020/05/22 02:38]
hepsim17
+++ hepsim:jas4pp [2021/02/17 16:15] (current)
hepsim17 [Reading ROOT files]
@@ Line 41: / Line 41: @@
   * Downloading and searching HepSim data
   * Processing ProMC files from HepSim
+  * Processing ROOT files created by the Delphes program for fast simulation
   * Running over SLCIO files with Geant4 simulated / reconstructed events.
   * Data analysis (jets, physics vectors, histogram packages)
-  * Visualisation of reconstructed events using Wired4 display
+  * Visualization of reconstructed events using Wired4 display
-You can find more details in [[https://atlaswww.hep.anl.gov/hepsim/description.php|HepSim manual]].
+You can find more details in [[https://atlaswww.hep.anl.gov/hepsim/doc/doku.php|HepSim manual]].
@@ Line 195: / Line 196: @@
 Also, look at concrete example of how to analyze single particles in [[:fcs:eic:intro|this section]].
+======  Reading ROOT files ======
+Jas4pp natively reads commonly used objects and data structures from [[https://root.cern/ | ROOT files]]  (versions 3, 4, 5 and 6).
+ROOT files can be loaded using the Jas4pp menu [File]-[Open data source]-[Root file] (*.root).
+In addition, one can work with ROOT files using Python/Jython or Groovy scripts.
+One can find some examples in the directory "examples/root".  Here is a Jython/Python example showing how to read a ROOT tree:
+<hidden Show example of a Python code here>
+<code python>
+from  hep.io.root.interfaces import TTree
+from  hep.io.root import RootFileReader
+reader = RootFileReader("ntuple_tree.root")
+tree = reader.get("tree");
+maxevents=tree.getEntries()
+leaves = tree.getLeaves()
+nrleaves=leaves.size()
+print "Nr of events=",maxevents
+print "Nr of leaves=",nrleaves
+print "Leaves:"
+for l in xrange( nrleaves ):
+   print "Leaf=",(leaves.get(l)).getName()
+print "Run over events"
+f0=leaves.get(0);
+f1=leaves.get(1);
+f2=leaves.get(2);
+for i in xrange(tree.getEntries()):
+      print f0.getValue(i), f1.getValue(i), f2.getValue(i)
+</code>
+</hidden>
+The example directory also shows how to read histograms.
+Similar examples can be made using Java or Groovy scripting.
+The supported ROOT interfaces are:
+<hidden show more details on ROOT interfaces here>
+TArrayC
+TArrayD
+TArrayF
+TArrayI
+TArray
+TArrayL
+TAttAxis
+TAttFill
+TAttLine
+TAttMarker
+TAxis
+TBasket
+TBranchClones
+TBranchElement
+TBranch
+TBranchObject
+TClonesArray
+TCollection
+TDatime
+TDirectory
+TFile
+TGraph
+TH1D
+TH1F
+TH1
+TH2D
+TH2F
+TH2
+TKey
+TLeafB
+TLeafC
+TLeafD
+TLeafElement
+TLeafF
+TLeafI
+TLeaf
+TLeafL
+TLeafObject
+TLeafO
+TLeafS
+TList
+TMap
+TNamed
+TObjArray
+TObject
+TProfile
+TSeqCollection
+TStreamerBase
+TStreamerBasicPointer
+TStreamerBasicType
+TStreamerElement
+TStreamerInfo
+TStreamerLoop
+TStreamerObjectAny
+TStreamerObject
+TStreamerObjectPointer
+TStreamerString
+TString
+TTree
+</hidden>
+One can browser histogram (or ROOT objects) using this:
+<code python>
+import rootio
+rootio.HBrowser("histograms_root5.root") # browser and plot ROOT histograms
+rootio.Browser("histograms_root5.root")  # browser for ROOT objects
+</code>
+You will see the browsers:
+{{:hepsim:browser_histograms.png?300|Histogram browser}}
+{{:hepsim:root_browser.png?300|Object browser}}
+The script that call these browsers  can be put into Jython or Groovy files and executed as binary programs.
+To read ROOT files from Delphes simulations, use
+[[https://atlaswww.hep.anl.gov/asc/jas4pp/api/rootio/Delphes.html|Delphes class]] and its "get" methods,
+getFloat, getDouble, getInt, and getBool. But first, explore the Delphes ROOT file using the browser shown above.
+Here is an example that uses high-level classes to read transverse momentum (PT) and pseudorapidity (ETA) of Monte Carlo particles:
+<hidden Click here to show  a Python code to read Delphes files>
+<code python>
+from  hep.io.root import RootFileReader
+from rootio import *
+reader = RootFileReader("mg5_ttbar_Njet_001.root" )
+tree = reader.get("Delphes");
+maxevents=tree.getEntries()
+branches=tree.getBranches()
+print "Nr of events=",tree.getEntries()
+print "Nr of branches=",branches.size()
+print "Branches:"
+for l in xrange( branches.size()  ):
+   print "Branch=",l," name=",(branches.get(l)).getName()
+particles=tree.getBranch("Particle") # get  generator particles
+ptEvents=Delphes.getFloat(particles,"PT")   # get PT array
+etaEvents=Delphes.getFloat(particles,"Eta") # get ETA array
+from jhplot import *
+h1 = H1D("PT of particles",100, 0, 100)
+h2 = H1D("Eta of particles",100, -4, 4)
+for i in xrange(tree.getEntries()):
+       pt,eta=ptEvents[i],etaEvents[i]
+       for j in xrange(len(pt)):
+           h1.fill(pt[j])
+           h2.fill(eta[j])
+c=HPlot("pT",600,300,2,1)
+c.visible()
+c.setAutoRange()
+c.draw(h1)
+c.cd(2,1)
+c.setAutoRange()
+c.draw(h2)
+</code>
+</hidden>
+{{:hepsim:pt_eta_delphes.png?300|}}
+<note warning>Reading Delphes trees is an experimental feature. Under study </note>
 ====== Using GUI mode ======
@@ Line 339: / Line 512: @@
   * S.Chekanov (ANL, main developer)
   * E.May (ANL, debugging, Wired4)
+  * Gagik Gavalian (JLab)