Hi Giacomo,
The list of TGraph is only generated with option "cont".
See some comments in the relevant part of your code below
Rene Brun
onetwojet_rateI.Draw("CONT List"); //must be option "cont" not "cont1"
c2->Update(); //to force the effective painting
TObjArray *contours =
(TObjArray*)gROOT->GetListOfSpecials()->FindObject("contours");
Int_t ncontours =contours->GetSize();
printf("%d \n",ncontours);
//for (Int_t i=0; i<ncontours;i++) {
TList *list = (TList *)(contours->At(8)); //some contours may have 0
TGraph
printf("%d \n",list->GetSize());
TGraph *gr111 = (TGraph *)list->First();
printf("%d \n",gr111->GetFillColor());
On Tue, 6 Aug 2002, Giacomo Bruno wrote:
>
> On Mon, 5 Aug 2002, Rene Brun wrote:
>
> > Could you send me evidence that the option (cont List) returning
> > a list of TGraphs does not work (C++ macro and a Root file)?
>
>
> Hi Rene,
> sorry for the late answer, but my delay was due to some changement of
> behaviour I have observed as I was preparing the macro and the root file
> for you to check.
>
> You can find the macro and the root file under
>
> /afs/cern.ch/user/g/gbruno/public/For_Rene/
>
> Part of the problems (unpredictable behaviour) have disappeared as soon as
> I got rid of a library that I used to load at the beginning of the macro,
> but that I was not actually using to make that particular contour plot.
> This library had
> been compiled separately with the compiler used by the reconstruction
> program ORCA of CMS (gcc 2.95.2). I have not understood yet why this
> caused problems but I guess it could be linked to some conflict
> since in the library I was using the class TObjArray.
>
> However after removing the load of this library I have still error
> messages.
> Actually I have now realized (after restarting root from
> scratch), that the error occurs at different lines according to the past
> of the root session.
>
> The last error I get is
>
> Error: illegal pointer to class object contours 0x0 219 FILE:Rene.C
> LINE:95
>
> Before restarting root, this line was not giving any problem. Instead I
> could not get access to contour 9 , the last of the 10 I set. The other
> contours seemed to be ok.
> The error was
>
> Error: illegal pointer to class object contours 0x0 219 FILE:Rene.C
> LINE:101
> *** Interpreter error recovered ***
>
>
> I hope you will be able to help me
>
> cheers
> Giacomo
>
>
>
>
> >
> > Rene Brun
> >
> > On Mon, 5 Aug 2002, Giacomo Bruno wrote:
> >
> > >
> > > Hi
> > > I would like to draw a 2-d histogram in contour format showing the levels
> > > with lines of different colours. I get the lines as expected, but then I
> > > would also like to draw a legend.
> > > To this aim I need to retrieve in some way the colours id
> > > of the lines. On the user's guide 3.02 at page 42 it is explained how to
> > > access the TGraph objects that are created when drawing a contour plot, however when I
> > > tried it everything happened (sometimes crashes, sometimes wrong results and
> > > almost always running the same code gave different results). I was then obliged to
> > > guess the colours and set them by hand. Does anyone have an idea on how to
> > > solve this problem?
> > > Thanks in advance
> > >
> > > cheers
> > > Giacomo
> > >
> > >
> > >
> > > -----------------------------------------
> > > | Giacomo BRUNO |
> > > | |
> > > | CERN |
> > > | EP Division |
> > > | |
> > > | mail: 40-2-B20 |
> > > | C.E.R.N. |
> > > | CH - 1211 Geneva 23 |
> > > | Switzerland |
> > > | e-mail: Giacomo.Bruno@cern.ch |
> > > | phone: +41 22 76 71624 |
> > > -----------------------------------------
> > >
> > >
> > >
> >
> >
>
> -----------------------------------------
> | Giacomo BRUNO |
> | |
> | CERN |
> | EP Division |
> | |
> | mail: 40-2-B20 |
> | C.E.R.N. |
> | CH - 1211 Geneva 23 |
> | Switzerland |
> | e-mail: Giacomo.Bruno@cern.ch |
> | phone: +41 22 76 71624 |
> -----------------------------------------
>
>
>
>
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