#!/usr/bin/perl
#
#

##########################################
#  plot x^2 to represent the potential energy of a spring-like force
  
  my($output_file, $term_options);

  # get the arguments
  $output_file = "quad_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 '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 xzeroaxis  lw 3.5 \n";
#  printf CMDFILE "set yzeroaxis  lw 3.5 \n";
  printf CMDFILE "set ylabel 'Potential energy (J) '  \n";
  printf CMDFILE "set xlabel 'Displacement (nm) ' \n";
  printf CMDFILE "set title '' \n";
#  printf CMDFILE "set label  '{/Symbol w_0} ' at 8.8,-0.5 \n";

  $cmd = "plot [-1.0:1.0][] 3.2E-15*x*x  ";
  $cmd .= "        with lines ls 1 lw 6 t '' ";

  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 -rotate 90 $psfile $giffile";
    printf "cmd is ..$cmd.. \n";
    $ret = `$cmd`;
  }



exit 0;