Filling Histogram with weight

Filling histograms

An histogram is typically filled with statements like:

       h1->Fill(x);
     h1->Fill(x,w); fill with weight
     h2->Fill(x,y)
     h2->Fill(x,y,w)
     h3->Fill(x,y,z)
     h3->Fill(x,y,z,w)

这里的w是weight.