#!/usr/bin/perl
#



############################################################################
# create a file with GNUPLOT commands, then execute GNUPLOT to read
#   from that file.
#
# usage:  make_graph   outfile_file_name  set_term_options
#
  
  my($output_file, $term_options);

  # get the arguments
  $output_file = "fall2015.ps";
  $term_options = "postscript color enhanced";

  $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";
  printf CMDFILE "set grid \n";
  printf CMDFILE "set key top right \n";
  printf CMDFILE "set ylabel 'Period SQUARED (seconds-squared) \n";
  printf CMDFILE "set xlabel 'Length of pendulum (cm)' \n";
  printf CMDFILE "set title 'pendulum experiment Nov 16, 2015' \n";
  
  $cmd = "plot [-10:160] 'fall2015_pend.dat' using ";
  #$cmd = "plot 'spr2014_pend.dat' using ";
  $cmd .= " (\$1):(\$2*\$2):(\$2*\$2)*(2*(\$3/\$2)) ";
  $cmd .= " with yerrorbars  lt 1 pt 1 lw 4 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`;
  }