Re: AddFriend

See the doc of TTree::AddFriend functionS. To add a friend tree having the same name "tree" as in your case, do

void Compare2trees(void){

   TFile *f0 = new TFile("ntuple0.root");    TTree *tree0 = (TTree*)f0->Get("Tree");

   TFile *f1 = new TFile("ntuple1.root");    TTree *tree1 = (TTree*)f1->Get("Tree");

   tree->AddFriend(tree1,"tree1");

   tree->Draw("tree.ph_pt-tree1.ph_pt");

}

Rene Brun

Henso Abreu wrote:
> Dear Rene,
>
> I did what you recommend to me, but I did not have success.
>
> I send you my code and also I remember you that my variable ph_pt is a
> vector.
>
> Thank you into advance,
>
> Henso
>
> void Compare2trees(void){
>
> TFile *f0 = new TFile("ntuple0.root");
> TTree *tree0 = (TTree*)f0->Get("Tree");
>
> TFile *f1 = new TFile("ntuple1.root");
> TTree *tree1 = (TTree*)f1->Get("Tree");
>
> tree0->AddFriend("tree1");
>
>
> tree0->Draw("tree0->ph_pt-tree1->ph_pt");
>
> }
>
>
> Rene Brun wrote:
>> see documentation of TTree::AddFriend. You can specify the treename
>> in TTree::Draw, eg
>> // tree.AddFriend("ft1","friendfile1.root");
>> // tree.AddFriend("ft2","friendfile2.root");
>> // tree.Draw("var:ft1.v1:ft2.v2");
>> // tree.Draw("var:ft1.var:ft2.var")
>>
>> When your Trees have the same name, specify an alias using the
>> special AddFriend function
>> TFriendElement* TTree::AddFriend(TTree* tree, const char* alias,
>> Bool_t warn)
>>
>>
>> Rene Brun
>>
>> Marc Escalier wrote:
>>> Dear roottalkers,
>>>
>>> I have a question from Henso, who is not yet subscribed to this forum
>>>
>>> Let's suppose we have two trees (tree0 and tree1) which have a same
>>> given variable name inside : "myvariable"
>>>
>>> how to do something like
>>>
>>> tree0->Draw("myvariable_from_tree0 - myvariable_from_tree1")
>>>
>>> and how to do something like :
>>>
>>> mydifference = tree0->GetValueOf n-th event of
>>> myvariable_from_tree0 - myvariable_from_tree0"
>>>
>>> AddFriend would be useful if the two tree would have different name
>>> of variables, but here, the variables have the same names
>>>
>>> (where myvariable is the same name in the two trees)
>>>
>>> thanks in advance for Henso
>>>
>>> ================
>>>>>>> TFile *f0 = new TFile("f0.root");
>>>>>>> TTree *tree0 = (TTree*)f0->Get("tree");
>>>>>>> TFile *f1 = new TFile("f1.root");
>>>>>>> TTree *tree1 = (TTree*)f1->Get("tree");
>>>>>>>
>>>>>>> // get variable pt of tree0 and keep it in float pt0
>>>>>>> // get variable pt of tree0 and keep it in float pt1
>>>>>>> //we wish :
>>>>>>> // pt0 - pt1 .
>>>>>>>
>>>>>>> }
>>>
>>
>
Received on Mon Jan 25 2010 - 12:28:38 CET