[ROOT] Change of cut not noticed

[Daniel Barna]

Hi Rene,
I am using v2.25 on a linux pc.
These are the steps I made:

TFile file("file.root");
TTree *t = (TTree *)file.Get("tree");
t->Draw("x:z");

//Now I create a TCutG with the graphics editor, and rename it to "mycut".

t->Draw("x:z","mycut");
// it works fine, only points in the selected area appear on the screen

gROOT->Delete("mycut");
t->Draw("x:z");

// now I create another TCutG with the graphics editor, and rename
// it again to "mycut"

t->Draw("x:z","mycut");

// at this step TTree::Draw seems to use the previous cut, the produced
// plot is the same as before

Daniel

> Hi Daniel,
> I do not understand this problem. Which version are you using ?
> What do you mean by "deleting the cut from the current directory" ? Could
> you provide a snapshot of your code with the calls to create the cut,
> delete it ? Note that I am currently on holidays with sporadic access to
> the internet.
>
> Rene Brun
>
> On Thu, 27 Jul 2000, Daniel Barna wrote:
>
> > Hi Rooters,
> > I created a TCutG object by setting it's points in a
> > fuction. It worked fine when I used it in a selection of TTree::Draw.
> > Later I deleted this TCutG object from the root directory, and created a
> > new TCutG object with the same name, but TTree::Draw
> > didn't recognize the change: it used still the old cut.
> > What is the right way to avoid such a case?
> > Thanks
> > Daniel
>
>
>

[Rene Brun]

Hi Daniel,
The Probleme in your piece of code is with gROOT->Delete("mycut").
This statement will no nothing if your cut is not drawn on the screen.
When a TCutG object is created , it is automatically added to the list
of special ROOT objects, that you can retrieve with a statement like:
TCutG *mycut = (TCutG*)gROOT->GetListOfSpecials()->FindObject("mycut")

In order to delete your cut, you should first get a pointer to it via the
avove statement, then do
delete mycut;

You can also delete a cut via the mouse using the contextmenu item "Delete"
when your cut is drawn on the screen.

see http://root.cern.ch/root/html/TCutG.html

Rene Brun