Calculating average using a perl script


Ok here is the basic perl script for calculating average.

I assume you know how to run the script if you dont ( I will put up a tutorial later so for now dig around in other forms )

Perl Script for calculating average from another file

#!/usr/bin/perl
#calculate averate from a file

use strict;

my $total = 0;
my $count =0;
while (my $line = <>) {
      $total +=$line;
      $count ++=;
}
print "Average = ", $total / $count, "\n";

So the  explaniation for the above code is…

use strict; – allow to find simple mistakes

to find the $average need to calculate

my $total

and the total number of lines

my $count

At the begining of the loop these values are 0.

therefore define the inital value

my $total  = 0;
my $count =0;

So now what you need to do this read each line andadd each value consequtively.

while (my $line = <>) {
   $total += $line;
   $count ++=;
 }
print "Average = ", $total / $count, "\n";

Read the first line.  Then add then and the value read to the total inital value  of 0.

   $total = $line + $total

calculate the total

   $count = $count + 1

calculate the total number of lines read
this can be written in short form as below

   $total += $line;
   $count ++=;

then go back in loop adding value conseutively until there are no more lines to read and then print the line

print "Average = ", $total / $count, "\n";

Hope this is clear I will put a anotated diagram up with more explanation later on.

3 thoughts on “Calculating average using a perl script”

  1. Very good!, I was looking for something like this to do some calculations, like here the average (mean), median, sd, range (max – min values) and quartiles (1st and 3ed) from a file.
    I hope you can help me.

    Thanks.

    1. Thank you for the comment.

      You just gave me the idea for a blog post 🙂

      What exactly do you need? Have you got any perl scripts that you tried? I’m quite new to perl so bare with me on this.

      1. hello Shavin,
        Yeah I’ve got one Perl Script with the commands to calculate some Statistics.
        but, it’s a mess and, sine I’m new in Perl, I cant get it working.
        here is it, It may have some redundancies.
        }
        close(FILEHANDLE);

        ####################################################
        # mean, sum and size #
        ####################################################

        my ( $N, $sum ) = ( 0, 0 );
        # create a loop, and generate a counter (still dont
        # which loop I should use
        $array[$x-1];
        $N++;
        $sum += $array[$x-1];
        # outside the loop to calculate the mean
        $mean = $sum/$N;
        print “$mean\n”;

        ####################################################
        # minimum and the maximum #
        ####################################################

        ($min = 0, $max = 0);
        $max = $array[$x-1]
        if ($max < $array[$x-1]), (my@sorted = sort { $a $b } @samples)
        {
        print join(” “,@sorted);
        };

        ####################################################
        # median #
        ####################################################

        if ($N % 2==1) {
        $median = $sorted[int($N/2)];
        }
        print $sorted[$N/2];

        else {
        $median = ($sorted[$N/2] + $sorte [($N/2)-1]);
        $med = $median/2;
        print “$med\n”;
        };

        #####################################################
        # quantiles 1º and 3º #
        #####################################################

        if $qt1 = $sorted[$r25-1] {
        print “\n”; # check this out
        };
        else $qt1 = $fr*($sorted[$ir] – $sorted[$ir-1]) + $sorted[$ir-1] {
        print “\n”; # check this out
        };

        #####################################################
        # variance #
        #####################################################

        for (my $i=0;
        $i<scalar(@samples);
        $i++)
        {
        $Var += ($samples[$i]-$mean)**2;
        $Var = $Var/($N-1);
        };

        #####################################################
        # standard error #
        #####################################################

        ($Std = sqrt($Var)/ sqrt($N));

        #####################################################

        print "$min\n";
        print "$max\n";

        print "$median\n";
        print "$qt1\n";
        print "$var\n";
        print "$std\n";

        exit(0);

        Thanks, for replay.

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