Laurent, In your example below, simply change the statement: nt->Draw("Krun"); to ch->Draw("Krun") and your program will work correctly. Rene Brun Laurent Mirabito wrote: > > Hello, > > I have the following problem using TChain > I created one TTree per run and I tried to Draw variable using TChain: > > root [4] TChain ch("nt") > root [5] ch.Add("Cluster20638.root") > root [6] ch.Add("Cluster20637.root") > root [7] ch.ls() > OBJ: TChainElement nt Cluster20638.root : 0 > OBJ: TChainElement nt Cluster20637.root : 0 > root [8] nt->Print() > Error: No symbol nt->Print() in current scope FILE:/tmp/17867haa LINE:1 > root [9] nt->Draw("Krun") > Error: No symbol nt->Draw("Krun") in current scope FILE:/tmp/17867iaa > LINE:1 > But when I open file by file it works > root [0] TFile f("Cluster20638.root") > root [1] f.ls() > TFile** Cluster20638.root > TFile* Cluster20638.root > KEY: TTree nt;1 An example of a ROOT tree > root [2] nt->Print() > ************************************************************************************ > *Tree :nt : An example of a ROOT > tree * > *Entries : 17430 : Total Size = 662542 bytes File Size = > 208130 bytes * > * : : Tree compression factor = > 4.12 * > ************************************************************************************ > *Branch :Krun : > Krun/I * > *Entries : 17430 : Total Size = 49994 bytes File Size = > 230 bytes * > *Baskets : 2 : Basket Size = 25000 bytes Compression= > 217.37 * > *..................................................................................* > *Branch :Kevt : > Kevt/I * > *Entries : 17430 : Total Size = 49994 bytes File Size = > 17564 bytes * > *Baskets : 2 : Basket Size = 25000 bytes Compression= > 2.85 * > *..................................................................................* > *Branch :Nclus : > Nclus/i * > *Entries : 17430 : Total Size = 49996 bytes File Size = > 6198 bytes * > *Baskets : 2 : Basket Size = 25000 bytes Compression= > 8.07 * > *..................................................................................* > *Branch :Idet : > Idet/i * > *Entries : 17430 : Total Size = 49994 bytes File Size = > 3309 bytes * > *Baskets : 2 : Basket Size = 25000 bytes Compression= > 15.11 * > *..................................................................................* > *Branch :Vclu : > Vclu/F * > *Entries : 17430 : Total Size = 49994 bytes File Size = > 22553 bytes * > *Baskets : 2 : Basket Size = 25000 bytes Compression= > 2.22 * > *..................................................................................* > *Branch :Noiclu : > Noiclu/F * > *Entries : 17430 : Total Size = 49998 bytes File Size = > 18954 bytes * > *Baskets : 2 : Basket Size = 25000 bytes Compression= > 2.64 * > *..................................................................................* > *Branch :Xclu : > Xclu/F * > *Entries : 17430 : Total Size = 49994 bytes File Size = > 22081 bytes * > *Baskets : 2 : Basket Size = 25000 bytes Compression= > 2.26 > > ... > > Any Ideas ? > Best regards > Laurent > -- > Laurent Mirabito > IPN Lyon
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