Plot multiple columns from txt file

[diabloi]

Hello guys, I started to use root to plot data.
I have a data3.txt file that is formatted in this way.
t1,x1,y1,z1
t2,x2,y2,z2
…
tn,xn,yn,zn

0,-3.995401863840999e-10,0,-3.995401905274687e-10
9.999999999999999e-12,4.997762014691721e-10,9.999999999999999e-12,4.995327580028662e-10
2e-11,3.637950016230157e-09,2e-11,3.637187318331949e-09
3e-11,8.978101986779303e-09,3e-11,8.976621362139576e-09

I implemented this code, pop up the windows, but i don’t see the graph. should be three signal in the same graph. Where do i wrong?

void plot2(){
ifstream infile; // input file handle
infile.open(“data3.txt”); // opening input data file

double x,y,z,w; // variable for storing data points while reading
vector x_list, y_list, z_list, w_list; // vectors for storing data points x and y

while (infile>>x>>y>>z>>w) { // reading data point in while loop
x_list.push_back(x); // adding data point x to vector
y_list.push_back(y); // adding data point y to vector

z_list.push_back(z);        // adding data point z to vector
w_list.push_back(w);        // adding data point w to vector

}

TMultiGraph *mg = new TMultiGraph(); // declaring TMultiGraph pointer

TGraph *g1 = new TGraph(x_list.size(), &x_list[0], &y_list[0]); // creating TGraph for first and second columns
TGraph *g2 = new TGraph(x_list.size(), &x_list[0], &z_list[0]); // creating TGraph for first and third columns
TGraph *g3 = new TGraph(x_list.size(), &x_list[0], &w_list[0]); // creating TGraph for first and fourth columns

g1->SetLineColor(kRed); // set color for first graph
g2->SetLineColor(kGreen); // set color for second graph
g3->SetLineColor(kBlue); // set color for third graph

mg->Add(g1);
mg->Add(g2);
mg->Add(g3);

mg->Draw(“AL”);
mg->GetXaxis()->SetTitle(“X”);
mg->GetYaxis()->SetTitle(“Y”);
mg->SetTitle(“Plot of Second, Third, and Fourth Columns vs First Column”);
}

[couet]

Welcome to the ROOT forum.

data3.txt

0                     -3.995401863840999e-10 0                     -3.995401905274687e-10
9.999999999999999e-12  4.997762014691721e-10 9.999999999999999e-12  4.995327580028662e-10
2e-11                  3.637950016230157e-09 2e-11                  3.637187318331949e-09
3e-11                  8.978101986779303e-09 3e-11                  8.976621362139576e-09

plo2.C

void plot2(){
   ifstream infile; // input file handle
   infile.open("data3.txt"); // opening input data file

   double x,y,z,w; // variable for storing data points while reading
   vector<double> x_list, y_list, z_list, w_list; // vectors for storing data points x and y

   while (infile>>x>>y>>z>>w) { // reading data point in while loop
      x_list.push_back(x); // adding data point x to vector
      y_list.push_back(y); // adding data point y to vector
      z_list.push_back(z);        // adding data point z to vector
      w_list.push_back(w);        // adding data point w to vector
   }

   TMultiGraph *mg = new TMultiGraph(); // declaring TMultiGraph pointer

   TGraph *g1 = new TGraph(x_list.size(), &x_list[0], &y_list[0]); // creating TGraph for first and second columns
   TGraph *g2 = new TGraph(x_list.size(), &x_list[0], &z_list[0]); // creating TGraph for first and third columns
   TGraph *g3 = new TGraph(x_list.size(), &x_list[0], &w_list[0]); // creating TGraph for first and fourth columns

   g1->SetLineColor(kRed); // set color for first graph
   g2->SetLineColor(kGreen); // set color for second graph
   g3->SetLineColor(kBlue); // set color for third graph

   mg->Add(g1);
   mg->Add(g2);
   mg->Add(g3);

   mg->Draw("AL");
   mg->GetXaxis()->SetTitle("X");
   mg->GetYaxis()->SetTitle("Y");
   mg->SetTitle("Plot of Second, Third, and Fourth Columns vs First Column");
}

Gives:

[diabloi]

I am expecting 3 lines, but in my case is opening just the windows without signals.
this should be the result of the first two columns. I used excel to shows the result.

[diabloi]

I got the problem…
my data are like this:

0,1,2,3
1,2,3,4
2,3,4,5
3,4,5,6
with space is working.
0 1 2 3
1 2 3 4
2 3 4 5
3 4 5 6
How can i manage this comma “,” point during the reading?

[couet]

Yes thats what i showed in the corrected example I sent you. I reformatted the data file (without commas) and I fixed a mistake in the script.

[diabloi]

is there any way to plot the file without modifying the source data?

[couet]

Plotting the file is not the issue, but reading it is the question. That’s not a ROOT issue but a C++ one. And there quite a lot of details on the web regarding the reading of CSV (Comma Separated Value) files:

CSV File Management Using C++ - GeeksforGeeks

How can I read and parse CSV files in C++?

Etc …

[dastudillo]

You can also use this constructor to read the file (instead of ifstream), selecting the columns (using the appropriate separator) you want for each graph:
https://root.cern/doc/master/classTGraph.html#ab902beb9e0463b225f0f384b6826a434

[diabloi]

I tried this way, but is not working.
I tried also this command: TGraph* gr = new TGraph(“data3.txt”,“%lg %lg %lg %lg”,“,”);

void plot1() {

TGraph* gr = new TGraph(“data3.txt”,“%lg,%lg,%lg,%lg”);
gr->SetTitle(“Distance Time Graph;Time (s); Distance (m)”);

gr->SetMarkerColor(4);
gr->SetLineWidth(3);
gr->SetLineColor(4);
gr->GetXaxis()->CenterTitle(true);
gr->GetYaxis()->CenterTitle(true); //

TCanvas *c1 = new TCanvas(“c1”, “c1”, 83, 137, 894, 713);
c1->SetFillColor(0); // background frame color white
c1->SetGridx(); // set vertical grid
c1->SetGridy(); // set horizzontal grid
c1->SetFrameFillColor(0); // background graph color
c1->SetFrameLineWidth(3);

gr->Draw(); // plotting graph on canvas

}

[couet]

TGraph has only two vectors X and Y (see documentation) your file has four columns. It can be read that way with TGraphErrors (see documentation). Assuming the last two columns are the errors:

auto  gr = new TGraphErrors("data3.txt","%lg,%lg,%lg,%lg");

[diabloi]

I found this other workaround. what do you think?

void plot1() {

//TGraph* gr = new TGraph(“data3.txt”,“%lg,%lg,%lg,%lg”);
// Create a TCanvas to draw the multi-graph
TCanvas *c = new TCanvas(“c”, “Multi-Graph Example”, 800, 600);

// Create a TMultiGraph object
TMultiGraph *mg = new TMultiGraph();

// Read the data file
ifstream file(“data3.txt”);
if (!file) {
cerr << “Error: unable to open file data3.txt” << endl;
return;
}

// Create two TGraph objects to store the data
TGraph *graph1 = new TGraph();
TGraph *graph2 = new TGraph();
TGraph *graph3 = new TGraph();

// Read the data file and fill the TGraph objects
double x, y1, y2, y3;
while (file >> x >> y1 >> y2 >> y3) {
graph1->SetPoint(graph1->GetN(), x, y1);
graph2->SetPoint(graph2->GetN(), x, y2);
graph3->SetPoint(graph2->GetN(), x, y3);
}

// Add the TGraph objects to the TMultiGraph
mg->Add(graph1);
mg->Add(graph2);
mg->Add(graph3);

// Customize the multi-graph
mg->SetTitle(“Multi-Graph Example”);
mg->GetXaxis()->SetTitle(“X Axis”);
mg->GetYaxis()->SetTitle(“Y Axis”);

// Draw the multi-graph
mg->Draw(“ALP”);

// Update the canvas
c->Update();
}

[couet]

Yes, that’s a possibility. The first column represents the x-values, and the last three columns are different y-values that you can plot on separate graphs grouped in a multigraph.

[couet]

@diabloi

graph1->SetPoint(graph1->GetN(), x, y1);
graph2->SetPoint(graph2->GetN(), x, y2);
graph3->SetPoint(graph2->GetN(), x, y3);

You can also do:

graph1->AddPoint(x, y1);
graph2->AddPoint(x, y2);
graph3->AddPoint(x, y3);