Problems with SetNpx and SetNpy in TGraph2D

ROOT
1

Hi,

I am plotting a data file using TGraph2D:

TGraph2D *g = new TGraph2D("resultado.dat"); g->Draw("surf1z"); gStyle->SetPalette(1.);

and I am getting a graph with a peak value of approximately 20000 (this is consistent with the highest value in the data file).

But when I set the parameters SetNpx and SetNpy:

g->SetNpx(14.); g->SetNpy(14.);

The peak value is approximately 12000, using the same data file.

anyone knows what is happening ??, I wish your help.

Thanks

Manuel

P. S: Anyone knows how to load an image in this forum.

2

Which ROOT version are you using ?
This should be fixed now …

3

I use the ROOT Version 5.26/00 14 December 2009

4

That’s quite recent.
Can you send an example showing the problem ?

5

In this case, I need to send an image, but I don’t know how to load an image in this forum.

Do you know??

6

I do not need an image I need a macro (with may be a data file) reproducing the problem.

7

well,

I use the code:

[code] TGraph2D *g = new TGraph2D(“resultado.dat”);
g->SetTitle(“Fonte simulada”);

g->GetXaxis()->SetTitle(“Pixel-X”);
g->GetXaxis()->CenterTitle();
g->GetXaxis()->SetTitleOffset(1.5);
g->GetXaxis()->SetNdivisions(13.);

g->GetYaxis()->SetTitle(“Pixel-Y”);
g->GetYaxis()->CenterTitle();
g->GetYaxis()->SetTitleOffset(1.5);
g->GetYaxis()->SetNdivisions(13.);

g->GetZaxis()->SetTitle(“Contagem”);
g->GetZaxis()->CenterTitle();
g->GetZaxis()->SetTitleOffset(1.4);

g->Draw(“surf1z”);
gStyle->SetPalette(1.);

[/code]

where the data file “resultado.dat” is :

1 1 221 2 1 159 3 1 5 4 1 257 5 1 125 6 1 -53 7 1 -33 8 1 -111 9 1 -121 10 1 -41 11 1 -149 12 1 -187 13 1 -109 1 2 175 2 2 -21 3 2 -43 4 2 31 5 2 165 6 2 -297 7 2 -175 8 2 -73 9 2 -185 10 2 -129 11 2 -59 12 2 149 13 2 233 1 3 81 2 3 25 3 3 135 4 3 131 5 3 -1 6 3 -81 7 3 -105 8 3 121 9 3 -25 10 3 211 11 3 109 12 3 9 13 3 37 1 4 19 2 4 123 3 4 -135 4 4 229 5 4 37 6 4 -39 7 4 25 8 4 65 9 4 -81 10 4 91 11 4 171 12 4 -305 13 4 -189 1 5 127 2 5 65 3 5 -155 4 5 -135 5 5 185 6 5 3 7 5 207 8 5 -21 9 5 95 10 5 83 11 5 137 12 5 -61 13 5 -111 1 6 125 2 6 -55 3 6 -27 4 6 5 5 6 -7 6 6 133 7 6 41 8 6 -65 9 6 -243 10 6 75 11 6 -207 12 6 99 13 6 -127 1 7 -17 2 7 -303 3 7 -93 4 7 -135 5 7 19 6 7 -37 7 7 21711 8 7 245 9 7 -53 10 7 -53 11 7 149 12 7 21 13 7 229 1 8 -107 2 8 -341 3 8 49 4 8 -75 5 8 159 6 8 -79 7 8 39 8 8 29 9 8 -71 10 8 127 11 8 -173 12 8 37 13 8 -63 1 9 79 2 9 -3 3 9 -73 4 9 123 5 9 -117 6 9 113 7 9 203 8 9 9 9 9 75 10 9 325 11 9 71 12 9 -97 13 9 -97 1 10 79 2 10 243 3 10 -179 4 10 23 5 10 189 6 10 -139 7 10 125 8 10 93 9 10 1 10 10 -209 11 10 -129 12 10 -183 13 10 205 1 11 9 2 11 165 3 11 55 4 11 -225 5 11 139 6 11 -185 7 11 -89 8 11 -153 9 11 115 10 11 89 11 11 75 12 11 215 13 11 221 1 12 5 2 12 -151 3 12 -117 4 12 155 5 12 41 6 12 -199 7 12 -91 8 12 37 9 12 -93 10 12 -123 11 12 -101 12 12 -93 13 12 -75 1 13 -131 2 13 129 3 13 11 4 13 -27 5 13 -3 6 13 -71 7 13 -249 8 13 139 9 13 -149 10 13 121 11 13 15 12 13 -59 13 13 189

I am getting a graph with a peak value of approximately 20000, consistent with the highest value in the data file.

But when I add the parameters to the code above:

g->SetNpx(14.); g->SetNpy(14.);

The highest value of the peak in the graph changes, now is the approximately 12000 and I don`t know what is happening.

8

What you see is normal.
When you plot using the option surf1 you are not plotting the graph2d directly but an histogram filled according to the triangle sitting above each bin.
Going to less bin you are losing precision and some triangle are not use. Specially in region which high gradient like peaks.
To plot the graph2d directly use the TRI, TRI1 … etc options

9

Thank you very much, your suggestion work…

Manuel