Re: Read TTree from file

TTree::ReadFile is using the names that you specify in the branch descriptor.
If you want to have the branch name with a different name, procedd as follows:
 TTree* Tree = new TTree( "Test", "Test" );  int Len;
 double ar[2];

 Tree->Branch("Len",&Len,"Len/I");
 Tree->Branch("Array",ar,"Array[2]/D");
 Tree->ReadFile( "Array2.txt");

in this case you should remove the branch descriptor line from your Array1.txt

Rene Brun

Thomas Lauf wrote:
> Thanks for the quick answer!
> I can reproduce your lines also on my machine, no problem here.
> But a thing that does not work is this:
>
> root [0] TTree* Tree = new TTree( "Test", "Test" );
> root [1] Long64_t RetVal = Tree->ReadFile( "Array1.txt" );
> root [2] Double_t Array[2];
> root [2] Tree->SetBranchAddress( "Array", &Array )
> Error in <TTree::SetBranchAddress>: unknown branch -> Array
>
> I can read out the tree branch this way
> root [3] Tree->SetBranchAddress( "Array[2]", &Array )
> root [4] for( Int_t i=0; i<3; ++i ) {
> Tree->GetEntry(i);
> cout << Array[0] << " " << Array[1] << endl;
> }
> 1.1 2.1
> 3.1 4.1
> 5.1 6.1
>
> Somehow the name of the branch gets handled differently.
> When the branch descriptor is "Array[2]", it is displayed this way
> under TTree::Print(), but not under TTree::Show().
> TTree::Scan() delivers in my case:
>
> root [5] Tree->Scan()
> Error in <TTreeFormula::TTreeFormula>: Index 2 for dimension #1 in
> Array[2].Array[2].Array is too high (max is 1)
> ************************************
> * Row * Len * Array[2]. *
> ************************************
> * 0 * 2 * *
> * 1 * 2 * *
> * 2 * 2 * *
> ************************************
> (Long64_t)3
>
> but only under ROOT 5.25, using 5.20 I get
> root [3] Tree->Scan()
> ***********************************************
> * Row * Instance * Len * Array *
> ***********************************************
> * 0 * 0 * 2 * 1.1 *
> * 0 * 1 * 2 * 2.1 *
> * 1 * 0 * 2 * 3.1 *
> * 1 * 1 * 2 * 4.1 *
> * 2 * 0 * 2 * 5.1 *
> * 2 * 1 * 2 * 6.1 *
> ***********************************************
> (Long64_t)6
>
>
> Thomas
>
> Rene Brun wrote:
>> I cannot reproduce your problem with any version of ROOT (I tried
>> 5.22,5.25 and 5.26).
>> The result of your 2 commands = tree.Print gives
>>
>> root [0] TTree* Tree = new TTree( "Test", "Test" );
>> root [1] Long64_t RetVal = Tree->ReadFile( "Array1.txt" );
>> root [2] Tree.Print()
>> ******************************************************************************
>>
>> *Tree :Test :
>> Test *
>> *Entries : 3 : Total = 1621 bytes File Size
>> = 0 *
>> * : : Tree compression factor =
>> 1.00 *
>> ******************************************************************************
>>
>> *Br 0 :Len :
>> Len/I *
>> *Entries : 3 : Total Size= 634 bytes One basket in
>> memory *
>> *Baskets : 0 : Basket Size= 32000 bytes Compression=
>> 1.00 *
>> *............................................................................*
>>
>> *Br 1 :Array[2] :
>> Array[2]/D *
>> *Entries : 3 : Total Size= 705 bytes One basket in
>> memory *
>> *Baskets : 0 : Basket Size= 32000 bytes Compression=
>> 1.00 *
>> *............................................................................*
>>
>>
>>
>> and if you do, eg
>> root [3] Tree.Show(0)
>> ======> EVENT:0
>> Len = 2
>> Array = 1.1,
>> 2.1
>> everything is Ok
>>
>> Rene Brun
>>
>> Thomas Lauf wrote:
>>> Hello,
>>>
>>> if I apply this little script
>>>
>>> {
>>> TTree* Tree = new TTree( "Test", "Test" );
>>> Long64_t RetVal = Tree->ReadFile( "Array1.txt" );
>>> gROOT->ProcessLine("Tree->Print(\"toponly\"); > Array3.dat");
>>> }
>>>
>>> on the file Array1.txt which looks like this
>>>
>>> Len/I:Array[2]/D
>>> 2 1.1 2.1
>>> 2 3.1 4.1
>>> 2 5.1 6.1
>>>
>>> I would expect the resulting tree to have 2 branches named 'Len' and
>>> 'Array' of which the second one is an array of doubles with length 2
>>> and the file Array3.dat should look like this:
>>>
>>> ************************************************************************
>>>
>>> *Tree :Test :
>>> Test *
>>> *Entries : 3 : Total = 1601 bytes File Size =
>>> 0 *
>>> * : : Tree compression factor =
>>> 1.00 *
>>> ************************************************************************
>>>
>>> branch: Len 0
>>> branch: Array 0
>>>
>>> The script passes with no errors but the branch containing the array
>>> does not have the expected name, it is named 'Array[2]' as one can
>>> see in the real output:
>>>
>>> ************************************************************************
>>>
>>> *Tree :Test :
>>> Test *
>>> *Entries : 3 : Total = 1601 bytes File Size =
>>> 0 *
>>> * : : Tree compression factor =
>>> 1.00 *
>>> ************************************************************************
>>>
>>> branch: Len 0
>>> branch: Array[2] 0
>>>
>>> What went wrong? How can I get ROOT to name the branch 'Array'?
>>> My research in the documentation so far was futile...
>>>
>>> I am using ROOT 5.20/00 on linux. I have tested this example also under
>>> ROOT 5.25/02, but it failed there too.
>>>
>>> Thanks for any advice
>>>
>>> Thomas
>>>
>>
>
>
Received on Tue Jan 12 2010 - 14:07:36 CET