Re: [ROOT] How to draw a TMarker at a given position

From: Rene Brun (
Date: Mon Apr 12 2004 - 12:58:29 MEST

Hi Jacek,

You must be using a version older than 3.10.
Support for log scales for low level primitives like markers and lines
was introduced in 3.10 only.

Rene Brun

Fri, 9 Apr 2004, Jacek M. 
Holeczek wrote:

> Hi,
> I've met the following problem.
> I have a TH2F with user specified bins (both in X and Y) which I draw in a
> pad :
> 	gPad->SetLogx(1);
> 	gPad->SetLogy(1);
> 	histo->Draw("cont4");
> What I get is a correctly drawn histogram and the newly created axes are:
> 	X from 1.0e-1 to 3.0,
> 	Y from 1.0e-5 to 1.0e-3.
> Now I would like to Draw a TMarker in the "min" of this histogram (let's
> say x=1.0, y=1.0e-4), so I try :
> 	TMarker *m = new TMarker(1.0, 1.0e-4, 29)
> 	m->Draw();
> The problem is ... either the marker is not drawn at all or it appears on
> a completely crazy position.
> If I "Inspect" the marker which is displayed, I get some coordinates, but
> I cannot find any function which translates between these coordinate
> systems (none of them is NDC[0,1]).
> Could you, please, help me,
> Thanks in advance,
> Best regards,
> Jacek.

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