void compare2analytic()
{
tn->Draw("v:c1","","goff");
TGraph *gn = new TGraph(tn->GetSelectedRows(), tn->GetV2(), tn->GetV1());
ta->Draw("v:c1","","goff");
TGraph *ga = new TGraph(ta->GetSelectedRows(), ta->GetV2(), ta->GetV1());
gStyle->SetPadLeftMargin(0.11); gStyle->SetPadRightMargin(0.01);
gn->SetMarkerColor(kBlue);
gn->SetMarkerStyle(kCircle);
gn->SetMarkerSize(0.8);
gn->SetTitle(";Radial position [cm];Potential [V]");
gn->GetXaxis()->SetRangeUser(0,1);
gn->GetYaxis()->SetRangeUser(0,900);
gn->Draw("ap");
ga->SetLineColor(kRed);
ga->Draw("l");
TLegend *l = new TLegend(0.6,0.6,0.8,0.8);
l->AddEntry(ga,"Analytic","l");
l->AddEntry(gn,"SOR","p");
l->Draw();
gPad->Print("s1d.png");
}