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--- hepsim:jas4pp [2020/11/05 14:21]
hepsim17
+++ hepsim:jas4pp [2021/02/13 23:12]
hepsim17 [Reading LCIO files]
@@ Line 195: / Line 195: @@
 Also, look at concrete example of how to analyze single particles in [[:fcs:eic:intro|this section]].
+======  Reading ROOT files ======
+Jas4pp natively reads ROOT files including files created using ROOT 6 (ROOT3, 4 and 5 are also supported). For example, one can read ROOT trees/ntuples.
+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:
+{{:asc:browser_histograms.png?300|Histogram browser}}
+{{:asc: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.
+Jas4pp does not support ROOT files with complex objects created using ROOT 6, i.e. TH1D, TH2D and TGraph.  Under investigation.
 ====== Using GUI mode ======