void ternary_plot()
{
    TCanvas *cnv = new TCanvas("cnv", "Ternary plot", 600, 600);
    cnv->Range(-0.2, -0.2, 1.2, 1.2);

    const UInt_t n = 3;           //      C                   A            B
    const double samples[][3] = {{/*Organic matter*/0.8, /*Clay*/0.1, /*Sand*/0.1}, 
                                 {/*Organic matter*/0.5, /*Clay*/0.4, /*Sand*/0.1},
                                 {/*Organic matter*/0.1, /*Clay*/0.4, /*Sand*/0.5}};

    const Double_t yC = TMath::Sqrt(3.) / 2;

    Double_t xs[n] = {};
    Double_t ys[n] = {};

    for (UInt_t i = 0; i < n; ++i) {
        xs[i] = samples[i][2] + samples[i][0] / 2;
        ys[i] = yC * samples[i][0];
    }

    TGraph *ternaryPlot = new TGraph(n, xs, ys);    
    ternaryPlot->Draw("*");

    TGaxis *a1 = new TGaxis(0., 0., 0.5, yC, 0., 100.);
    a1->Draw();

    TGaxis *a2 = new TGaxis(0.5, yC, 1., 0., 0., 100.);
    a2->Draw();

    TGaxis *a3 = new TGaxis(1., 0., 0., 0., 0., 100.);
    a3->Draw();
}