[ROOT] Re: quick question

From: Daniel Holmes (Daniel.Holmes@cern.ch)
Date: Fri Nov 29 2002 - 11:39:06 MET


Hi Rene,

hmm, no i don't think this was quite what i wanted (or i have not
sufficiently understood it.

In short what i have is a 2-D array (converted from hbook->root) stored in
1 leaf
ie for each phioffset[i] (i=1->100) there are 1000 entries.. i need to be
able to return any given entry for a given phioffset[i].

((if i do t->Draw("phioffset[3]"); then i get a 1-D histo with 1000
entries)) 

the code :
   TLeaf *l_phioffset = t->GetLeaf(("phioffset");
   l_phioffset->GetBranch()->GetEntry(5); //to read entry 5
   double phioffset = l_phioffset->GetValue();

works fine for a 1-D array but in fact i need to be able to define an
index of phioffset before i loop over its entries.

If this was what you sent in your last email then perhaps you could
clarify exactly how i should input the code as i don't seem to be able to
run it without errors,..

many thanks for your ongoing support,

Dan.



CMS-Bristol
http://cern.ch/dan.holmes

On Thu, 28 Nov 2002, Rene Brun wrote:

> Hi Dan,
> 
> You can do
>   double phioffset3 = l_phioffset->GetValue(3);
> or
>   double *phioffset = (double*)l_phioffset->GetValuepointer();
>   and then access pihioffset[3];
> 
> Rene Brun
> 
> On Thu, 28 Nov 2002, Daniel Holmes wrote:
> 
> > thanks Rene,
> > 
> > How do i change the code below so i can read a 2-D, array.. i can plot :
> > t->Draw("phioffset[3]"); using the "phioffset" leaf.
> > 
> > cheers,
> > 
> > Dan.
> > 
> > 
> > > With your example, you can do
> > >   TLeaf *l_phioffset = t->GetLeaf(("phioffset");
> > >   l_phioffset->GetBranch()->GetEntry(5); //to read entry 5
> > >   double phioffset = l_phioffset->GetValue();
> > > 
> > > Rene Brun
> > > 
> > 
> > 
> 
> 



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