#!/usr/bin/perl
#

  
  my($output_file, $term_options);

  # FK4 stars only
  $output_file = "compare_curves_a.ps";
  $term_options = "postscript color enhanced 'Helvetica,18' ";

  $cmdfile = "gnuplot.in";
  
  open (CMDFILE, ">$cmdfile") || die("can't open $cmdfile for writing");
  printf CMDFILE "set output '$output_file' \n";
  printf CMDFILE "set term $term_options \n";

  #  revert to some oldish default colors 
  printf CMDFILE "set style line 1 lt rgb 'red' lw 3  \n"; 
  printf CMDFILE "set style line 2 lt rgb 'sea-green' lw 3  \n"; 
  printf CMDFILE "set style line 3 lt rgb 'blue' lw 3  \n"; 
  printf CMDFILE "set style line 4 lt rgb 'cyan' lw 3  \n"; 
  printf CMDFILE "set style line 5 lt rgb 'violet' lw 3  \n"; 


  

  printf CMDFILE "set grid \n";
  printf CMDFILE "set key top right \n";
  printf CMDFILE "set ylabel 'Orbital speed (km/s) '  \n";
  printf CMDFILE "set xlabel 'Distance from galactic center (kpc) ' \n";
  printf CMDFILE "set title 'Comparison of rotation curves '\n";
  
  $cmd = "plot [0:10][0:600]  ";
  $cmd .= "   './exercise_curve.dat' using 2:5 ";
  $cmd .= "       with points ls 1 ps 2 pt 6 t 'Keplerian' ";
  $cmd .= " , ";
  $cmd .= "   './exercise_curve.dat' using 2:4 ";
  $cmd .= "       with points ls 3 ps 2 pt 3 t 'measured HI' ";

  printf CMDFILE "$cmd \n";
  printf CMDFILE "set output \n";
  printf CMDFILE "quit \n";
  close(CMDFILE) ;
  
  $retval = `gnuplot < $cmdfile`;
  printf "retval is ..%s..\n", $retval;
  
  if ($term_options =~ /postscript/) {
    $psfile = $output_file;
    $giffile = $psfile;
    $giffile =~ s/.ps/.png/;
    $cmd = "convert -flatten -background white -rotate 90 $psfile $giffile";
    printf "cmd is ..$cmd.. \n";
    $ret = `$cmd`;
  }




exit 0;