Filling a TGraph with strings on axis label

ROOT
3

Although as couet said this is not intended by root it is still possible because the TGraph class uses an internal TH1 for drawing so all possibilities of a TH1 are more or less available for TGraphs. Assuming your vecors are of the std::vector type I’ve written you a short macro that does what you want. I names the vecors simply y_vals and x_labels. The problem is that you still have to set a numeric x-value, because otherwise root does not know where on the x-axis a specific string has to be drawn. In my example I just enumerate the points from 1 to Number of Points, which I assume is what you intended:

std::vector<Double_t> y_vals;
std::vector<std::string> x_labels;

// Fill the vectors here

TGraph* tg = new TGraph(TMath::Min(y_vals.size(), x_labels.size())); // Create the TGraph object

for (Int_t i = 0; i < TMath::Min(y_vals.size(), x_labels.size()); i++) { // Loop over all entries
    tg->SetPoint(i, i + 1., y_vals[i]); // Set The point itself
    tg->GetXaxis()->SetBinLabel(tg->GetXaxis()->FindBin(i + 1.), x_labels[i].c_str()); // Find out which bin on the x-axis the point corresponds to and set the bin label
}

tg->Draw("AP"); // Draw the TGraph

Hope this helps you. I tested it and it worked like I expected it to.

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