TEntryList intersection and operators

[wiso]

Why the intersection betweent two TEntryList is not implemented? For example if I have 2 selections and I want to know the number of events that pass all the selection?

Now in python I’m doing

def intersection(a,b):
   c = TEntryList(a)
   aa = TEntryList(a)
   aa.Subtract(b)
   c.Subtract(aa)
   return c

c is the intersection of a and b. a and b are not modified.

Can you implement the operator+, operator- in the TEntryList class? so I can write something like this:

TEntryList a,b,c;
a.Enter(1); a.Enter(2); a.Enter(3);
b.Enter(3); b.Enter(4); b.Enter(6);

c = a+b;  // c contains 1 2 3 4 5 6
c = a-b;  // c contains  1 2 
c = a.Intersection(b)  //why modify a?  or better
c = a*b   // c contains 3

[brun]

see functions Add, Subtract and Merge.
See examples in $ROOTSYS/test/stressEntryList.cxx

Rene

[wiso]

[quote=“brun”]see functions Add, Subtract and Merge.
See examples in $ROOTSYS/test/stressEntryList.cxx

Rene[/quote]

There is not intersection. From ther documentation:

Operations on entry lists

* Add() - if the lists are for the same tree, adds all the entries of the second list to the first list. If the lists are for different trees, creates a TEntryList with 2 sublists for each TTree. If the lists are for TChains, merges the ones for the same trees and adds new sublists for the TTrees that were not included in the first TEntryList
* Subtract() - if the lists are for the same TTree, removes the entries of the second list from the first list. If the lists are for TChains, loops over all sub-lists
* GetEntry(n) - returns the n-th entry number
* Next() - returns next entry number. Note, that this function is much faster than GetEntry, and it's called when GetEntry() is called for 2 or more indices in a row. 

Intersection? Simmetric difference? And I think it’s more clear do: c = a+b, instead a.Add(b); c = a; // a is modified, I don’t want this!

[brun]

Could you provide these missing operators and functions? you seem to have a test case.

Rene

[wiso]

[quote=“brun”]Could you provide these missing operators and functions? you seem to have a test case.

Rene[/quote]

You can implement:

const TEntryList TEntryList:operator+(const TEntryList &other) const
// return a TEntryList with the events in that are in *this OR in other
const TEntryList TEntryList:operator-(const TEntryList &other) const
// return a TEntryList with the events in that are in *this BUT NOT in other
const TEntryList TEntryList:operator*(const TEntryList &other) const
// return a TEntryList with the events in that are in *this AND in other

my work is:

1. get a tree with signal events and a tree with backgroud events
2. consider only a subset of these trees identified by a TCut subset (for example only triggered events, but it’s more complicated)
3. do a lot of selections on this events (each selections is a TCut), compute efficienties on signal and on backgroud, compute S/N
4. graph the selected events (signal and BK) for all the selections

I prefer a load and shoot approach: first I compute what events pass a selections, for every selection, and I compute what events pass the subset condition. I compute an array of TEntryList, one for each selections TCut, and one TEntryList for the subset Cut.

Then I must do the insersection between the selection TCut and the subset TCut.

Then I print the numbers of events, efficienties, S/N in a tabular form. These values are calculated from EntryList[n].GetN()

Then I draw the istogram using the TEventList previously computed (tree.SetEventList(EntryList[n]); tree.Draw(“branch”) for every n)

you can say: you can use

entries = tree.Draw("branch",selectionCut[n] && subsetCut) for every n

but I prefer to separate the drawing from the computing of the events that pass the selection, because my program is more complicated than this, for example, I want to calculate the efficienties of my selection varing the cuts. Maybe I don’t want to Draw the istogram… so I’m using a simple function that convert a TCut to an TEntryList, but this TEntryList must be insersecated with the subsetEntryList.

[pcanal]

Hi,

[quote]const TEntryList TEntryList:operator+(const TEntryList &other) const
// return a TEntryList with the events in that are in *this OR in other
const TEntryList TEntryList:operator-(const TEntryList &other) const
// return a TEntryList with the events in that are in this BUT NOT in other
const TEntryList TEntryList:operator(const TEntryList &other) const
// return a TEntryList with the events in that are in *this AND in other[/quote]

This is a new request and to improve the system and get those implemented sooner, maybe you can propose a complete (and tested) implementation for those?

Thanks,
Philippe.