splines_test.C

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/// \file
/// \ingroup tutorial_graphs
/// \notebook
/// Examples of use of the spline classes.
///
/// \macro_image
/// \macro_code
///
/// \author Federico Carminati
 
void splines_test(Int_t np = 23, Double_t a = -0.5, Double_t b = 31)
{
   // array of points
   Double_t *xx = 0, *yy = 0;
   TSpline3 *spline3 = 0;
   TSpline5 *spline5 = 0;
   TLine *line5, *line3;
   TText *text5, *text3, *textn;
   char text[20];
   const Double_t power = 0.75;
 
   // Define the original function
   TF1 *f = new TF1("f", "sin(x)*sin(x/10)", a - 0.05 * (b - a), b + 0.05 * (b - a));
   // Draw function
   f->Draw("lc");
 
   // Create text and legend
   Double_t xx1, yy1, xx2, yy2, dx, dy;
   gPad->Update();
   gPad->GetRangeAxis(xx1, yy1, xx2, yy2);
   dx = xx2 - xx1;
   dy = yy2 - yy1;
   line5 = new TLine(xx1 + dx * 0.3, yy1 + dy * 1.02, xx1 + dx * 0.38, yy1 + dy * 1.02);
   line5->SetLineColor(kRed);
   line5->SetLineWidth(2);
   text5 = new TText(xx1 + dx * 0.4, yy1 + dy * 1.03, "quintic spline");
   text5->SetTextAlign(12);
   text5->SetTextSize(0.04);
   line3 = new TLine(xx1 + dx * 0.67, yy1 + dy * 1.02, xx1 + dx * 0.75, yy1 + dy * 1.02);
   line3->SetLineColor(kGreen);
   line3->SetLineWidth(2);
   text3 = new TText(xx1 + dx * 0.77, yy1 + dy * 1.03, "third spline");
   text3->SetTextAlign(12);
   text3->SetTextSize(0.04);
   textn = new TText(xx1 + dx * 0.8, yy1 + dy * 0.91, " ");
   textn->SetTextAlign(12);
   textn->SetTextSize(0.04);
   textn->Draw();
 
   // Draw legenda
   line5->Draw();
   text5->Draw();
   line3->Draw();
   text3->Draw();
 
   for (Int_t nnp = 2; nnp <= np; ++nnp) {
 
      // Calculate the knots
      if (xx)
         delete[] xx;
      xx = new Double_t[nnp];
      if (yy)
         delete[] yy;
      yy = new Double_t[nnp];
      for (Int_t i = 0; i < nnp; ++i) {
         xx[i] = a + (b - a) * TMath::Power(i / Double_t(nnp - 1), power);
         yy[i] = f->Eval(xx[i]);
      }
 
      // Evaluate fifth spline coefficients
      Double_t eps = (b - a) * 1.e-5;
      if (spline5)
         delete spline5;
      spline5 = new TSpline5("Test", xx, f, nnp, "b1e1b2e2", f->Derivative(a), f->Derivative(b),
                             (f->Derivative(a + eps) - f->Derivative(a)) / eps,
                             (f->Derivative(b) - f->Derivative(b - eps)) / eps);
 
      spline5->SetLineColor(kRed);
      spline5->SetLineWidth(3);
 
      // Draw the quintic spline
      spline5->Draw("lcsame");
 
      // Evaluate third spline coefficients
      if (spline3)
         delete spline3;
      spline3 = new TSpline3("Test", xx, yy, nnp, "b1e1", f->Derivative(a), f->Derivative(b));
 
      spline3->SetLineColor(kGreen);
      spline3->SetLineWidth(3);
      spline3->SetMarkerColor(kBlue);
      spline3->SetMarkerStyle(20);
      spline3->SetMarkerSize(1.5);
 
      // Draw the third spline
      spline3->Draw("lcpsame");
 
      sprintf(text, "%3d knots", nnp);
      textn->SetTitle(text);
      gPad->Update();
 
      //
      gSystem->Sleep(500);
   }
}