Dear Monks,
Once again I need your kind help. I am trying to calculate sum of column-3 by window size of column-2 in the following example. In this example I would like to divide positions in column-2 into 20 base pair wide windows as below:

window_of_col-2     positions(col-2)    sum of col-3 (coverage) based 
+on window
---------------     --------            ---------------
1-20                1,4,7               9
21-40               22,24,38            21 
41-60               44,50,57,60         85
61-80               65                  30

And, I want to print the results as below:
window SUM
20  9
40  21
60  85
80  30

[download]

I spent a good amount of time on this, and I feel pretty stupid already. I tried range operator and tried to add a counter for window size, but could not make it work. Only the thing I can do is following that calculates sum of col-3 but not by window size. I would appriciate any help or pointers. Thanks.

#!/usr/bin/perl
use warnings;
use strict;
use 5.010;

my $total = 0;
while (<DATA>){
    chomp;
    my ($chr, $pos, $coverage) = split /\t/;
    $total += $coverage;   
}
say $total;

#-------------------------
#data format:
#chr positon_on_DNA coverage
__DATA__
chr    1    2
chr    4    2
chr    7    5
chr    22    5
chr    24    6
chr    38    10
chr    44    10
chr    50    20
chr    57    25
chr    60    30
chr    65    30

[download]

In reply to How to calculate sum of a column by window size based on another column by rnaeye

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