TGraph with unix time as X entries

ROOT
1

Hi,
I’m creating a TGraph object from an ntuple that contains a “t” variable that is a unix time (seconds from 1970/01/01)

BrokStatusNtuple->Draw(“t:executing”,rangePeak,“goff”);
TGraph *grExecuting=new TGraph(BrokStatusNtuple->GetSelectedRows(),BrokStatusNtuple->GetV1(), BrokStatusNtuple->GetV2());

when I try to draw the graph it seems that some V1 values are rounded (probably due to scientific notation:
1.xxxxe+9 ) causing the fact that, for example, several x entries are treated as being the same (that could not be as V1 entries are all different and increasing).
I’ve found:
GetXaxis()->SetNoExponent(kTRUE);
method but it fix just the way label are displayed in the axis

Any suggestion?
thanks in advance for help

2

Attach your ROOT file with the “BrokStatusNtuple” here for inspection.

3

Hi,
yes probably there are some limits in the way I could fill an ntuple … I used UInt_t values but I see that they are stored in scientific notation and probably somehow rounded
debug.root (28.5 KB)

4

All leaves in your “broker” tree are “Float_t”, so up to 6 to 9 decimal digits precision.
You need to recreate you tree using (for relevant leaves), for example, “Double_t” values which give 15 to 17 decimal digits precision, or “UInt_t”, or “Long64_t”, or “ULong64_t”.
The simplest thing would be to use a “TNtupleD” instead of a “TNtuple”.

5

THANKS!!! really appreciated your suggestion
Pier Fortunato