#!/usr/bin/perl
#
# compavg.pl <col1> <file> [<file>,...]
# computes the average of column 1
# in the specified files, ignoring lines starting with # 
#
# Author: Austin Parker
# This code in the public domain -- feel free to modify to your hearts content.
# If you find a bug, tell me.
#
# The author makes no guarantees about the quality or effectiveness of this 
# code, and bears no responsibility should anything go wrong.
# 
 
$printOnlyCor = 0;
$c1 = shift @ARGV or die "usage: compavg.pl <col1> <file> [<file>,...]";
if ($c1 =~ "-p") {
    $printOnlyCor = 1;
    $c1 = shift @ARGV or die "usage: compavg.pl <col1> <file> [<file>,...]";
}

$avg = 0;
$n = 0;
foreach $file (@ARGV) {

    print "\nWorking on file $file\n" if ($printOnlyCor == 0);
    open IN, "<$file";
    while (<IN>) {
        next if /^#/;
        # get x and y.
        @vals = split /\s+/;
        $x = $vals[$c1];
        next unless $x=~/^[\.\d]*\s*$/;
        $n++;
        $avg += $x;
    }
    close IN;
}
$avg /= $n if $n > 0;
if ($printOnlyCor == 0) {
    print "\nAverage is $avg for $n samples\n";
} else {
    print "$avg";
}