This is a fairly straightforward task using hashes. First iterate over your first list and increment the value on that key, i.e.

my %hash = ();
foreach my $element (@list1) {
    $hash{$element}++;
}
[download]

Repeat for the second list, and voila, if a key has a value of 2, it's in both lists. Post some code, and then we can help you debug it.

Update: Or if you don't want to write any code, you could always use List::Compare::Functional.

I think you misread the O.P. This isn't about comparing lists, and your code snippet can't get there.

Maybe this will do:

use strict;
use warnings;

my @id1 = (1..5);
my @id2 = (11..15);

my %hash;
my %col_header;
my %row_header;

my $last = $#id1 > $#id2 ? $#id1 : $#id2;

for my $i (0..$last) {
    if ( defined( $id2[$i] ) ) {
        $col_header{$id2[$i]} = 1;
    }
    if ( defined( $id1[$i] ) ) {
        $row_header{$id1[$i]} = 1;
    }
    if ( defined( $id1[$i] ) and defined( $id2[$i] ) ) {
        $hash{$id1[$i]}{$id2[$i]} = 1;
    }
}

my @col_header = sort numeric keys %col_header;
my @row_header = sort numeric keys %row_header;

printf "%10s" x (@col_header + 1), "id1\\id2", @col_header;
print "\n";

for my $row ( @row_header ) {
    printf "%10s", "$row";
    for my $col ( @col_header ) {
        printf "%10s", ( exists( $hash{$row}{$col} ) ? "1" : "0");
    }
    print "\n";
}

sub numeric {
    $a <=> $b;
}
[download]

with output:

   id1\id2        11        12        13        14        15
         1         1         0         0         0         0
         2         0         1         0         0         0
         3         0         0         1         0         0
         4         0         0         0         1         0
         5         0         0         0         0         1
[download]

(I'll leave it to OMAR to turn this into a sub.)

Update: here's the read-from-STDIN version:

Read more... (1003 Bytes)

-QM
--
Quantum Mechanics: The dreams stuff is made of

Hi QM, Your code has bee very helpful. Afters days of searching I now finally found this post/site and has given me faith I can do what I need (only a Perl beginner/hacker) Wondering if you could please help me do somthing like this.. which counts and is additive on multiple line items.

id1    id2    int
208    10000    1
208    10000    7
207    10000    3
8517   1147    1
3551   1147    2

   id1\id2      1147     10000
       207         0         3
       208         0         8
      3551         1         0
      8517         1         2
[download]

I will be forever in your gratitude!

Hi QM, Your code has bee very helpful. Afters days of searching I now finally found this post/site and has given me faith I can do what I need (only a Perl beginner/hacker) Wondering if you could please help me do somthing like this.. which counts and is additive on multiple line items. id1 id2 int 208 10000 1 208 10000 7 207 10000 3 8517 1147 1 3551 1147 2 id1\id2 1147 10000 207 0 3 208 0 8 3551 1 0 8517 1 2 I will be forever in your gratitude!

Please have a look at How do I compose an effective node title? and at Markup in the Monastery.

Don't misuse <pre>-Tags here.

To your question: you're telling what you have as data source and what the desired result should look like.

But you don't show where you have your problems...

So, where's your problem hidden? What do you have problems with?

Are you looking for someone to write your code?

Update: You could do something like this (if you want to do it on your own):

• read data
  • read data file and ignore header line
  • chomp and split each line into two pieces
  • create an entry in a hash-of-hash (HoH); $hash{id1}->{id2} = 1;
  • store id2 in an array if not already in that array
• output:
  • for each key in %hash print that key; check for every entry in your array if an entry in the HoH exists, if so, print 1, if not, print 0.

By adjacency matrix, I assume you mean something like what is mentioned in this article?

In that article, there is no explicit listing of the values in the adjacency matrix.