Re: AddFriend

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 - 12:02:58 CET