TGraph2D set axis title

ROOT
1

Hi everybody,
I have I problem when I try to set axis title on my TGraph2D (I’m under windows). I tried the code below but it gives me a strange image (see the picture):

[code]TGraph2D *g1 = new TGraph2D(6);
g1->SetPoint(0,1,0,0);
g1->SetPoint(1,0,1,0);
g1->SetPoint(2,0,0,1);
g1->SetPoint(3,-1,0,0);
g1->SetPoint(4,0,-1,0);
g1->SetPoint(5,0,0,-1);

g1->SetMarkerStyle(20);
g1->SetMarkerColor(kBlue);
g1->SetMarkerSize(1.5);
g1->GetXaxis()->SetTitle(“X”);
g1->GetYaxis()->SetTitle(“Y”);
g1->GetZaxis()->SetTitle(“Z”);
g1->Draw(“P”);[/code]

2

Hi,

try with (slightly) more reasonable data, e.g.

TGraph2D *g1 = new TGraph2D(6);
g1->SetPoint(0,1,0,0);
g1->SetPoint(1,0,1,1);
g1->SetPoint(2,0,0,2);
g1->SetPoint(3,-1,0,3);
g1->SetPoint(4,0,-1,4);
g1->SetPoint(5,1,1,5);
   
g1->SetMarkerStyle(20);
g1->SetMarkerColor(kBlue);
g1->SetMarkerSize(1.5);
g1->GetXaxis()->SetTitle("X");
g1->GetYaxis()->SetTitle("Y");
g1->GetZaxis()->SetTitle("Z");
g1->Draw("P");

and your code should work…

Thomas

c1.gif696×472 8.59 KB

3

Hi schieti,

Thanks for your great help! I tried with many points and it works eccept with theses “non reasonables data”. But the problem is that the data that I will use will be “non reasonable”. (It’s a part of my application, it will show molecules in the space). So I would like to know if exists a way to correct it?
Another time thank you very much.

4

Ah, sorry, I misunderstood. Still, setting the same point (0,0) to two different values does seem very unreasonable to me, at least for a TGraph2D, molecule or not. It somehow defeats the purpose of a TGraph2D (as an interpolated surface defined by unevenly spaced points).

I would look for a class that is better suited for your molecules…

Thomas

g1->SetPoint(2,0,0,1);
g1->SetPoint(5,0,0,-1);  // define value of (0,0) again!!
5

Hi Thomas,
Thank you for your explanation and interest, you are right TGraph2D is not the best thing to molecules’s position in the space (I forget this particular, TGraph is for surfaces :slight_smile:, sorry).
So I would thank you very much if you find somenthing better than TGraph2D.
Cheers,
Louis

6

Again I think you should use TPolyMarker3D instead of TGraph2D. You are not using any of the features TGraph2D provides. All you do is 3D markers.

7

Hi,

I found this thread because I had the same issue - I guess I am also using the wrong class, I get lots of warnings that look like this:

Warning in TGraphDelaunay::Interpolate: Two of these three points are coincident 48 94 81

However, if I use TPolyMarker3D , I get the set of points but with no axis!

So - what is the way to create a plot of markers in 3 dimensions with valid axes?

thanks!
Peter

8

Can you provide a small example showing what you get ?

9

Hi,

I’ve attached two files - the first is a small TFile containing a TTree with some data. The second is a short script which just plots three of the parameters against each other and then adds titles to the axes.

When I run it I get multiple errors (e.g.)

Warning in TGraphDelaunay::Interpolate: Two of these three points are coincident 113 135 105

But the plot is still created - and looks as I expect - except that the axis titles are absent.

thanks
Peter
testGraph2D.C (1.52 KB)
data.root (15.2 KB)

10

Sorry I forgot to add that I am running root 5.30/02 on OS X 10.7.2 with gcc 4.2.1

thanks
Peter

11 
When I run it I get multiple errors (e.g.)

Warning in <TGraphDelaunay::Interpolate>: Two of these three points are coincident 113 135 105

I see the same. And it means what the message says: you have many similar points. That’s it …

12

Hi,

yes I am ok with that - but does it explain why the axis titles do not appear? Do they appear for you?

thanks for the help
Peter

13

No they don’t … actually the axis do not appear at all.

14

Oh … yes … I see… drop option A
A means “No axis” (see doc)

15

great thanks!