Hey, So I'm trying to make a lower triangular distance matrix in an itterative fashion. I had a function hd(a,b) which returns the distance between two objects a and b. I then want to iteratively add rows to this matrix as more objects are added, but I want to only add new rows, not recalculate the old ones. so I wrote this 
    $hd::size1 = scalar @{\@{$main::M[0]}};
    $hd::size  = $hd::size1 - 1;

    for ($hd::i=$hd::save; $hd::i<= $hd::size; $hd::i++) #this creates
+ and adds to the hd array
    {
        $hd::store= [];
        for ($hd::j=0; $hd::j < $hd::i; $hd::j++)
        {
            $hd::temp = &hd($main::M[0][$hd::i], $main::M[0][$hd::j]);
            print $hd::temp;
            print "\n";
            push $hd::store, $hd::temp;
        }
        push @{$main::hd}, $hd::store;
    }
$hd::save = $hd::size

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for reference, main::M stores all the objects, and $main::hd is initialized as [];, and hd::save is initialized at 1 and updated each time the loops completes with hd::save = hd::size; Whenever I follow this up with a module, it says the the first row of my matrix has no columns. but, when I use the following code (something I wrote for myself for self-reference) 
#!/usr/bin/perl
#ex2
use warnings;
use strict;
sub clust;


$main::hd=[[]];
$main::a = [0.25];
$main::b = [0.25,0.5];
$main::C = [1,0.75,0.75];
$main::hdt = 0.4;
$main::c = [];
$main::c1 = 1;
$main::c2 = 0.75;
$main::c3 = 0.75;
                #how to add elements to an array
push $main::c, $main::c1;
push $main::c, $main::c2;
push $main::c, $main::c3;
                #how to add arrays to arrays
push @{$main::hd}, $main::a;
push @{$main::hd}, $main::b;
push @{$main::hd}, $main::c;





&clust;
for ($loop::i=0; $loop::i<=3; $loop::i++)
{
    print $clust::cluster_ids->[$loop::i], "\n";
}



sub clust {
    use Algorithm::Cluster::Thresh;
    use Algorithm::Cluster qw/treecluster/;
    $clust::tree = treecluster(data=>$main::hd, method=>'a');
     $clust::cluster_ids = $clust::tree->cutthresh($main::hdt);    
}

[download]
The module works perfectly. I think the error is how I'm iteratively storing things. Any ideas? EDIT: The error was in my definition of hd::save. I orginally defined it as $hd::size, but that causes it to recalculate the last object from the previous time step. Changing it to $hd::save=$hd::size +1; fixed everything. This meant the matrix was not diagonal, it had weird kinks in it. Thanks everyone who helped!!!!!

In reply to Array storage issue by viored

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