Mark different regions in a 3D scatter plot

ROOT
1

Dear root people,

Now there is a 3-D scatter plot ( e.g. the distribution of 3 particles’ mass). I am trying to find a way to mark the different regions of this distribution.

for example, (|m1| < 20, |m2| < 20, |m3| < 20) and (40<|m1|<60, 40<|m2|<60, 40<|m3|<60) are two regions I would like to highlight.

I am wondering if I could set different marker color for these two parts or draw a 3-d cube to show the region, while, unfortunately, i’ve no idea about how to realize either of these methods.

It will be so kind if you could give me some ideas.

2

The 3D plot in that example may help you:
root.cern.ch/doc/master/ntuple1_8C.html

3

Thanks a lot.

I’ve tried that and it works but doesn’t look so good in my plot. For it is a combination of three normal distributions, this method works in the central area but for the side region as i mentioned in the question the difference of color can hardly be recognized.

So i wonder if it is possible to draw a box or just user-defined lines in a 3-d scatter plot to show these regions, or, does TShape work with TNuple?

[quote=“couet”]The 3D plot in that example may help you:
root.cern.ch/doc/master/ntuple1_8C.html[/quote]

4

Can you post the picture you get ?

5

Here is my plot and my source code, the points are generated by gRandom and the data will be just like it (the data is not available now).

void plot() {
    TCanvas *cvs = new TCanvas("cvs", "", 800, 600);
    gStyle->SetCanvasColor(0);
    gStyle->SetMarkerStyle(7);
    Int_t palette[5];
    palette[0] = 19;
    palette[1] = 46;
    palette[2] = 6;
    palette[3] = 30;
    palette[4] = 38;
    gStyle->SetPalette(5,palette);

    TNtuple *n = new TNtuple("n", "n", "x:y:z:color");
    for (Int_t i = 0; i < 10000; i++) {
        Float_t x, y, z;
        x=gRandom->Gaus(0, 10);
        y=gRandom->Gaus(0, 10);
        z=gRandom->Gaus(0, 10);
        n->Fill(x, y, z, setcolor(x, y, z));
    }
    for (Int_t i = 0; i < 3000; i++) {
        Float_t x, y, z;
        x=gRandom->Uniform(-40, 40);
        y=gRandom->Uniform(-40, 40);
        z=gRandom->Uniform(-40, 40);
        n->Fill(x, y, z, setcolor(x, y, z));
    }
    for (Int_t i = 0; i < 3000; i++) {
        Float_t x, y, z;
        x=gRandom->Gaus(0, 10);
        y=gRandom->Gaus(0, 10);
        z=gRandom->Uniform(-40, 40);
        n->Fill(x, y, z, setcolor(x, y, z));
        n->Fill(x, z, y, setcolor(x, z, y));
        n->Fill(z, y, x, setcolor(z, y, x));
    }
    n->Draw("x:y:z:color");
}

Int_t setcolor(Float_t x, Float_t y, Float_t z){
    Int_t color = 10;
    if (abs(x)<10 && abs(y)<10 && abs(z)<10) color = 50;
    if ((abs(x)>20 && abs(x)<40 && abs(y)<10 && abs(z)<10)||
        (abs(y)>20 && abs(y)<40 && abs(x)<10 && abs(z)<10)||
        (abs(z)>20 && abs(z)<40 && abs(x)<10 && abs(y)<10)) 
        color = 40;
    if ((abs(x)>20 && abs(x)<40 && abs(y)>20 && abs(y)<40 && abs(z)<10)||
        (abs(y)>20 && abs(y)<40 && abs(z)>20 && abs(z)<40 && abs(x)<10)||
        (abs(z)>20 && abs(z)<40 && abs(x)>20 && abs(x)<40 && abs(y)<10)) 
        color = 30;
    if (abs(x)>20 && abs(x)<40 && 
        abs(y)>20 && abs(y)<40 && 
        abs(z)>20 && abs(z)<40) 
        color = 20;
    return color;
}

I was working on the palette but it looks like a mess, while it’s pretty good on the x-y (or other projection) plane. Maybe it’s not a good idea to do this in a 3-d plot.

plot.png796×572 22.4 KB

6

It looks fine seems to me … what do you not like ? have you try to use transparency ?
root.cern.ch/doc/master/classTColor.html#C07

7

Well… i am not sure whether this picture is clear enough to show the locations of parts. Maybe i am being too demanding.

Thank you for your advice! Hope transparency will make it better.

8

I have turned to python for better looking plot. With matplotlib i was able to do this and i wonder if it’s possible to draw a similar scatter plot with ROOT.

figure_1.png800×600 79.3 KB

9

Yes there is also the option BOX in ROOT for 3D plots.