void ks_example()
{
  
  TH1* h = new TH1F( "h", "Gaussian", 20, -5, 5 );
  // h->FillRandom( "gaus", 100 );
  // h->Draw();
  TF1* f = new TF1( "f", "TMath::Freq(x)", -5, 5 );


  const UInt_t N = 20;
  Double_t val[N];
  Int_t    idx[N];
  for( UInt_t i = 0; i < N; ++i ) {
    val[i] = gRandom->Gaus();
    h->Fill( val[i] );
  }
  h->Draw();
  gPad->SaveAs( "ks_gauss.pdf" );

  TMath::Sort( N, val, idx, false );

  Double_t dmax = 0;
  UInt_t   imax = 0;
  Double_t bins[N+2];
  Double_t binc[N+1];

  bins[0]   = -5;
  bins[N+1] = 5;
  binc[0]   = 0;

  for( UInt_t i = 0; i < N; ++i ) {
    Double_t x  = val[idx[i]];
    Double_t F  = f->Eval( x );
    Double_t Fn = Double_t( i+1 ) / Double_t( N );
    bins[ i+1 ] = x;
    binc[ i+1 ] = Fn;
    Double_t D = fabs( F - Fn );
    if( D > dmax ) {
      dmax = D;
      imax = i;
    }
    cout << x << " " << F << " " << Fn << " " << D << " " << dmax << " " << imax << endl;
  }



  TH1* he = new TH1F( "he", "KS: CDFs", N+1, bins );
  he->SetFillColor( 0 );
  for( UInt_t i = 0; i < N+1; ++i ) {
    he->SetBinContent( i+1, binc[i] );
  }
  he->SetStats( kFALSE );
  he->Draw();

  f->Draw( "same" );

  gPad->SaveAs( "ks_compare.pdf" );


}