Problems with ntuples

Glen R. Salo (gsalo@mrcday.com)
Fri, 26 Mar 1999 19:27:08 -0500 (EST)

The macro below demonstrates the problem that I have been having with ntuples.
When I run the macro on my machine (Linux 2.0.36, 2.21.08) I get a histogram
displayed with the ranges going from -21 to -15. However, according to
GetMaximum and GetMinimum, the X range should really be from -20.5 to 20.5. Why
is the X axis set up incorrectly?

Interestingly, if I change nsamples to a smaller number, say 21, everything
works as expected.

Thanks for your help.

Glen

{

gROOT->Reset();

TNtuple *n = new TNtuple("ntuple","RSphere attachment data",
"xs:ys:zs:xe:ye:ze");

Float_t xs, ys, zs;
Float_t start, delt=1.;

Int_t nsamples = 41;

start = -nsamples*delt/2.;

for (Int_t i=0; i<nsamples+1; i++) {
for (Int_t j=0; j<nsamples+1; j++) {
for (Int_t k=0; k<nsamples+1; k++) {

xs = start + i*delt;
ys = start + j*delt;
zs = start + k*delt;

n->Fill(xs,ys,zs,i,j,k);

}
}
}

printf("min = %f\n",n->GetMinimum("xs"));
printf("max = %f\n",n->GetMaximum("xs"));
n->Draw("xs");

}

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Glen R. Salo g.r.salo@ieee.org
Mission Research Corporation (937)429-9261 Ext. 119
3975 Research Boulevard (937)429-2625 Fax
Dayton, Ohio 45430-2108

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