S.P. Wakely wrote:
>
> Hi ROOTers.
>
> I have noticed that you cannot dump to a 3D histogram using the TTree.Draw()
> function:
>
> Root> f = TFile("hsimple.root");
> Root> ntuple->Draw("pz>>h1");
> Root> ntuple->Draw("pz:py>>h2");
> Root> ntuple->Draw("pz:py:px>>h3");
>
> The first two work, but the last does not produce histogram h3.
Hi Scott,
Right, this is not yet implemented. I will code this addition.
>
> --
> Also, I have a question about the preferred technique for graphing functions
> of two variables.
>
> As far as I know, the only way to graph a function such as x+y=z right now
> would be to loop over the value of z to fill a 2-d histogram:
>
> TH2S *h2 = new TH2S("h2","2D Histo",10,0,10,10,0,10);
> for(int x=0;x<10;x++){
> for(int y=0;y<10;y++){
> for(int z=0;z<=(x+y);z++){
> h2->Fill(x,y);
> }
> }
> }
>
> h2->Draw("lego2");
>
> This works OK, as long as the z values are non-negative
> But is there a better way to do this?
You can create a 2-d function, example
TF2 f2("f2","x+y",0,10,0,10);
f2.Draw("surf1");
Rene Brun
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