/*
**  DrawQQ
**
**  Purpose:
**    Show how a qq plot could be constructed
**
**  Date:
**    20/8/09
**
**  Author:
**    Charles Bos
*/
#include <oxstd.h>
#include <oxdraw.h>
// #include <packages/gnudraw/gnudraw.h>

main()
{
  decl vY, vQE, vQN, iN, dS, vQ;
  
  iN= 1000;
  dS= 4;
  vY= dS*rann(1, iN);
  
  DrawQQ(0, vY, "Norm s=4", QQ_N, dS, 0); 
  
  vQ= range(.01, .99, .01);
  vQE= quantiler(vY, vQ);
  vQN= dS*quann(vQ);
  
  print (vQ|vQE|vQN);
  
  // Plot theoretical against empirical probabilities
  DrawTitle(1, "PP-plot");
  DrawXMatrix(1, probn(vQE/dS), "Theor", vQ, "Emp", 0, 2);

  // Plot empirical against theoretical quantiles
  DrawTitle(2, "QQ-plot");
  DrawXMatrix(2, vQN, "Theor", vQE, "Emp", 0, 2);
  ShowDrawWindow();  
}