in reply to how to convert two lists into adjacency matrix

As has been suggested before, please read Writeup Formatting Tips. In particular, you should be using <code> tags to preserve whitespace and <p> to break paragraphs.

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.

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Re^2: how to convert two lists into adjacency matrix
by QM (Parson) on Apr 14, 2009 at 19:38 UTC
    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

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      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!
[reply]
      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!
[reply]
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