Hi,
I have the need to get something really close to what was asked here: Scatter plot with vector associated to each point
Shortly: a set of scattered vectors to display.
The issue is that my vectors are 3D: for each vector I have 3 coordinates for the positions and 3 values for its components.
Is there a way to get such a picture?
There is no such predefined representation in ROOT but it does not seems very difficult to do. For the markers you can make a TGraph with the (x,y) points. For the little line segments it is a bit more complicated but basically it is a loop producing a set of TLine. If you have a small sample of your data I can try to provide you some example.
Yep… Dots were not an issue for me either, but for the vectors/segments…
Here’s an example: test.txt (30.6 KB)
Thank you. 
So you are looking for a plot in 3D ?
Yes.
I need to have an idea of how to classify vectors into some angular binning, so yes, I need a 3D plot.
You need to define properly the vector but the idea is the following:
void plot3dwithvector() {
auto g = new TGraph2D();
double x[10] = { 0.333168894052505 , 1.46091299058071E-08 , 2.24945768678708E-08 , 0.152351081371307 , 5.51142020910334E-09 , 5.69387808013744E-08 , 2.64541766270554E-09 , 5.13162241588816E-08 , 1.78169090592206E-09 , 0.007284481078386 };
double y[10] = { 1500.05798339844 , 1500.05798339844 , 1500.05798339844 , 1500.05798339844 , 1500.05798339844 , 1500.05798339844 , 1500.05798339844 , 1500.05798339844 , 1500.05798339844 , 1500.05798339844 };
double z[10] = { 0.918900966644287, -0.932851850986481, -0.380060702562332, -1.52324450016022, 0.094302758574486, -1.5516140460968, 0.801989138126373, 1.78688251972199, -2.29705429077148, 2.20811176300049};
for (int i = 0; i<10; i++) g->SetPoint(i , x[i], y[i], z[i]);
g->Draw("P0");
double ux[10] = {11.7526865005493 , 14.0614671707153 , 14.0148906707764 , 15.8330516815186 , 14.732702255249 , 13.1480436325073 , 13.8227872848511 , 15.4252738952637 , 13.5150909423828 , 15.0704441070557 };
double uy[10] = {0.999999768794254 , 0.999995963966835 , 0.999999542140503 , 0.999996438482454 , 0.999999880467112 , 0.999998747243802 , 0.999999695773325 , 0.999997365844202 , 0.999994719735028 , 0.999995373222123 };
double uz[10] = {-0.000498842739034 , -0.002375233219936 , 0.000518542365171 , -0.002600628184155 , -0.000466246623546 , -0.000749222934246 , -0.000105562685349 , 0.002096008975059 , -0.003230506321415 , 0.002058336278424 };
for (int j = 0; j<10; j++) {
auto *l3 = new TPolyLine3D(2);
l3->SetPoint(0 , x[j], y[j], z[j]);
l3->SetPoint(1 , ux[j], uy[j], uz[j]);
l3->Draw();
}
}
What do you mean by that?
I found out that I gave you a bad input file, but that doesn’t matter.
I’m not sure about what these do:
l3->SetPoint(0 , x[j], y[j], z[j]);
l3->SetPoint(1 , ux[j], uy[j], uz[j]);
It looks like you’re setting two point, which are like the starting and ending points for each line…?
I just took the 10 first lines of your file to build up a small example. The idea is to draw the points (circles) using a TGraph2D made with the x y z positions and then add the lines (vectors) on this plot using several TPolyLine3D made of 2 points. The first point a given polyline is the same as the circle position and the second point as to be computed properly. Right now I just took the ux uy uz but it does not seems to be right.
Now, for the second point, I simply do:
l3->SetPoint(1 , ux[j], uy[j], uz[j]);
You need to change this to have the correct end point of the lines.
Uhm… So yes, the two lines I quoted are starting and ending points.
This should work, from the mathematical point of view…
l3->SetPoint(1 , x[j]+ux[j], y[j]+uy[j], z[j]+uz[j]);
edit: no, It’s wrong also from the mathematical point of view! 
But I’m on it. 
Yes, I gathered that. I let you find the right formula.
Yup!
I do remember some algebra yet, despite my premature senility. 
Gotta fix a few things yet, but the main issue is solved.
Thank you couet.
Thank you a lot.
Why I can’t set a user range for the TGraph2D axes?
This is the code I wrote thanks to your help:
// .x trial.c("input.txt")
bool verb = 1; // verbose?
const string tab("\t");
const string blue("\033[1;34m"); // info
const string green("\033[1;32m"); // request
const string pink("\033[1;35m"); // test
const string red("\033[1;31m"); // errors
const string yellow("\033[1;33m"); // warnings
const string reset("\033[0m\e[0m");
double xMin(1498);
double xMax(1898);
double yMin(-6);
double yMax(6);
double zMin(1);
double zMax(199);
bool fileExist(const char *fileName) {
ifstream infile(fileName);
return infile.good();
}
TCanvas * generateCanvas(int cW = 800, int cH = 800) {
TCanvas * c = new TCanvas("c", "plot1d", cW, cH);
c->SetMargin(0.1, 0.1, 0.1, 0.1);
c->ToggleEventStatus();
// c->ToggleEditor();
return c;
}
void trial (string input)
{
// check if input file exist
if (!fileExist(input.c_str())) {
cerr << red << "ERROR :: file " << input.c_str() << " doesn't exist!" << reset << endl;
return 1;
}
// dummy variables. How to avoid them?
double x, y, z;
double ux, uy, uz;
vector<double> vx, vy, vz;
vector<double> vux, vuy, vuz;
int p;
string line;
// generate Canvas using external function
TCanvas * c = generateCanvas();
TGraph2D * g = new TGraph2D();
// overwrite log-scale settings
gPad->SetLogx(false);
gPad->SetLogy(false);
gPad->SetLogz(false);
if (verb) cout << "Index" << tab << "x:" << tab << tab << "y:" << tab << tab << "z:" << tab << tab << "ux:" << tab << tab << "uy:" << tab << tab << "uz:" << endl;
// read input file and populate v* and vu* vectors which are origins and components of vectors
ifstream fileInput (input.c_str());
while (getline(fileInput, line)) {
if (line[0] == '#' || line[0] == '\0') continue;
stringstream(line) >> p >> x >> y >> z >> ux >> uy >> uz;
if (verb) cout << p << tab << scientific << x << tab << y << tab << z << tab << ux << tab << uy << tab << uz << endl;
vx.push_back(x);
vy.push_back(y);
vz.push_back(z);
vux.push_back(ux);
vuy.push_back(uy);
vuz.push_back(uz);
// draw origins on TGraph2D
g->SetPoint(p , x, y, z);
}
if (verb) cout << blue << ++p << " points read from input file" << reset << endl;
// setting user range. Why this doesn't work!?
if (xMin != xMax) {
g->GetXaxis()->SetRangeUser(xMin, xMax);
if (verb) cout << blue << scientific << "User defined range for the x axis: [" << xMin << ", " << xMax << "]" << reset << endl;
}
if (yMin != yMax) {
g->GetYaxis()->SetRangeUser(yMin, yMax);
if (verb) cout << blue << scientific << "User defined range for the y axis: [" << yMin << ", " << yMax << "]" << reset << endl;
}
if (zMin != zMax) {
g->GetXaxis()->SetRangeUser(zMin, zMax);
if (verb) cout << blue << scientific << "User defined range for the z axis: [" << zMin << ", " << zMax << "]" << reset << endl;
}
g->Draw("p0");
// draw 'vectors'
for (size_t i = 0; i < vx.size(); ++i) {
TPolyLine3D * l = new TPolyLine3D(2);
l->SetPoint(0, vx[i], vy[i], vz[i]);
l->SetPoint(1, vx[i] + 100*vux[i], vy[i] + 100*vuy[i], vz[i] + 100*vuz[i]);
l->Draw("tri same");
}
return;
}
You can try that using this as input file: input.txt (30.2 KB)
Please note that I use these xMin, xMax, yMin, etc variables for setting the user range.
Does your example really works ? it gives me:
root [0] .x try.c("input.txt")
In file included from input_line_11:1:
try.c:35:6: error: expected unqualified-id
void try (string input)
^
root [1]
Sorry, I didn’t change the first comment.
You can run it by
.x trial.c ("input.txt")
Ok.
Btw do:
l->Draw();
no need for any option (see my initial code)
Yep…
I tried to get some different style. I failed.
You put some TGraph2D option into TPolyLine3D … it is normal it fail… have a look at the TPolyLIne3D options …
for the range:
g->GetHistogram()->GetXaxis()->SetRangeUser(xMin, xMax);
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