void test()
{

    TH2D *h2 = new TH2D("h2", "", 30, 0, 600, 50, 0, 500);
    h2->Sumw2();
    for (int _ = 0; _ < 10000; _++)
    {
        h2->Fill(gRandom->Gaus(200, 50), gRandom->Gaus(60, 30));
    }

    h2->Scale(1. / 100000);
    TProfile *hp = h2->ProfileX();
    cout << "bin2 error from tprofile: " << hp->GetBinError(2) << endl;

    TH1D *h1 = new TH1D("hh1", "hh1", 30, 0, 600);

    for (int i = 0; i < h2->GetNbinsX(); i++)
    {
        double sum = 0.;
        double averagey = 0.;
        double averagey2 = 0.;
        for (int j = 0; j < h2->GetNbinsY(); j++)
        {
            sum += h2->GetBinContent(i + 1, j + 1);
            double y = h2->GetYaxis()->GetBinCenter(j + 1);
            averagey += y * h2->GetBinContent(i + 1, j + 1);
            averagey2 += pow(y, 2.) * h2->GetBinContent(i + 1, j + 1);
        }
        if (sum > 0.0)
        {
            averagey /= sum;
            averagey2 /= sum;
            double error = (averagey2 - pow(averagey, 2.)) / sum;
            error = TMath::Sqrt(error);
            h1->SetBinContent(i + 1, averagey);
            h1->SetBinError(i + 1, error);
            cout << "bin " << i + 1 << "\t" << error << "\t" << error / TMath::Sqrt(100000) << endl;
        }
    }
}