#include "TFile.h"
#include "TTree.h"

void skimOneTree() {
    TFile *fin   = TFile::Open("twotrees.root");
    TTree *tree  = (TTree*)fin->Get("tree2");

    TFile *fout = 0;
    TTree *clone = 0;

    fout =  new TFile("onetree_fast.root", "RECREATE");
    clone = tree->CloneTree(-1, "fast");
    clone->Write();
    fout->Close();

    fout =  new TFile("onetree.root", "RECREATE");
    clone = tree->CloneTree();
    clone->Write();
    fout->Close();

    fin->Close();
}