Cut with arrays in a tree

ROOT
1

Hi everebody,

I have a tree t defined with this:

t->Branch(“Ah”, &event.Ah,“Ah/I”);
t->Branch(“Emch”,&event.Emch,“Emch[multiplicityh]/F”);

In a Canvas, I draw both Ah and Emch as 1-D histograms separately.
Imagine we have a tree t defined with only 1 event.

For example:
Ah=140;
Emch=[1,3,5];

When I draw Ah with any cut, it displays a graph with a pick at 140 and a height of 1.
But now, if a draw the same histogram but with a cut defined with “Emch>2”, it displays , for Ah, a pick at 140 but with a height of 2. It’s because the number of particles which have their Emch above 2 are twice, one with 3 and an other with 5. We obtain the number of values which obey the condition, so , 2 , and not the number of event, this last equals to 1.
I would like to obtain the number of events when the condition is respected. So, I expect the value 1.

What I have to do or add to have it?

Thank you.

2

Hi,

Instead of “Emch>2” use “Sum$(Emch>2)>=1”

Cheers,
Philippe.

3

Hi,

I replace Emch>2 by Sum$(Emch>2)>=1 in the cut string, it is better but it seems to miss few evenments, not to much but when I cut with parameters larger than values in the root files, the 2 graphs are not exactely the same. There is something like 16% of evenements lost.

What is the problem please?

Thanks

4

Hi,

Without seeing your data file, it is bit hard to tell :slight_smile:

Anyway my guess would be that you missing the events where multiplicityh is zero.

Cheers,
Philippe.

5

OK, you’re right , I replace Sum$(Emch>2)>=1 by Sum$(Emch>2)>=0
and it is perfect

thank you very much

6

:laughing: No there is still a problem.
When I have Sum$(Emch>2)>=0 , I can have all evenements but it cuts nothing>
And I have Sum$(Emch>2)>=1 , I lose evenements but it cuts.
I must add a condition I thing but I don’t see which one.
I think you’re write, I forgot the case when the array is void.
The condition " Sum$(Emch>)>=1" is only valable if the size of Emch > 0;
What for size of Emch =0 ?

Thanks

7

[quote]What for size of Emch =0 ?[/quote]The Sum$ is invalid and the condition is false. However this sounds like the correct result anyway. If there is no Emch then the is none greater than >2. What am I missing?

Philippe.

8

OK , that was I discover in fact. I had some other conditions to take in account the case multiplicityh ==0 and now it is ok.

Thank you for your help

R.