/* -*-ePiX-*- */
#include "epix.h"
using namespace ePiX;

P F(double x, double y)
{
  return P((x-y)*(x+y), 2*x*y);
}

int main()
{
  picture(P(-1,0),P(1,20), "6x6in");

  begin();

  // create a 2-column data file with 121 rows
  data_file DF(Cos, Sin, 0, M_PI, 120);

  legend L;
  plain(Black());
  fill(Blue(1.8));

  // act on first two columns; result doubles angles
  DF.transform(F);

  data_bins db(-1.05, 1.05, 21); // bins centered on -1, -0.9, ..., 0.9, 1
  db.read(DF.column(1));   // read col1
  db.bar_chart(db.pop());  // and plot, scaling to population

  L.fill_item("Population count"); // add a filled legend item

  label_color(Blue(1.2));
  v_axis_labels(P(xmin(), ymin()), P(xmin(), ymax()), 0.5*ysize(), P(-4,0), l);
  // superimpose plot of raw data
  screen raw(P(-1,-1), P(1,1));
  activate(raw);
  label_color(Red());
  DF.plot(DDOT);            // scatter plot
  L.mark_item(DDOT, "Data points");

  nofill();
  plain(Black(0.3));
  grid(1,10);

  v_axis_labels(P(1,-1), P(1,1), 4, P(4,0), r);

  //  DF.write("circle.dat");  // write to a disk file
  inset(P(-1,0), P(1,20));
  deactivate(raw); // polite but unnecessary

  L.draw(canvas().c(), P(0,0), c);

  pst_format();
  end();
}
