in reply to How would I sort a two-dimensional array by multiple columns?

And if you really want a subroutine... 
use Test::More qw/no_plan/;

my $unsorted = [
    [ qw/1  3  5  6  2/ ],
    [ qw/3  4  5  6  7/ ],
    [ qw/1  2  3  4  5/ ],
    [ qw/5  6  7  8  8/ ],
    [ qw/1  2  3  4  5/ ],
    [ qw/2  2  2  2  2/ ],
    [ qw/1  1  2  4  5/ ],
    [ qw/2  3  4  5  6/ ],
];

my $expected = [
    [ qw/1  1  2  4  5/ ],
    [ qw/1  2  3  4  5/ ],
    [ qw/1  2  3  4  5/ ],
    [ qw/1  3  5  6  2/ ],
    [ qw/2  2  2  2  2/ ],
    [ qw/2  3  4  5  6/ ],
    [ qw/3  4  5  6  7/ ],
    [ qw/5  6  7  8  8/ ],
];

my $sorted = sortSub($unsorted, 0, 1, 3);

is_deeply $sorted, $expected;

sub sortSub {
    my @array = @{ +shift };

    my @sorted = sort {
        for my $ix ( @_ ) {
            my $cmp = $a->[$ix] <=> $b->[$ix];
            return $cmp if $cmp;
        }
        return 0;
    } @array;
    return \@sorted;
}

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Update: Fixed a mistake spotted by dbmathis Narveson.

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Re^2: How would I sort a two-dimensional array by multiple columns?
by Narveson (Chaplain) on Mar 15, 2008 at 21:28 UTC
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      Yes, you're right. I'll update the node now.

      Thanks

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        There are subtle bugsdifferences in interpretation of the OP's request in both jettero and FunkyMonk's solutions.

        In essence, neither goes deep enough to resolve differences - jettero stops at the second element, and FunkyMonk stops after index 3.

        FunkyMonk - in your code, "@_" inside the sort is probably not what you think it is - at that point, @_ is still the parameter passed into "sortsub". Inside the sort itself, you only have $a and $b. The "@_" comes from the outer sub.

        Here is code with slightly modified data, that demonstrates the errors, and my proposed "correct" solution.

        Read more... (3 kB)
        Update: Updated based on ikegami's note below (return 0, not 1);
        Also updated FonkyMonk's sort - uses @_ instead of 0..@_.

        Update 2: The O.P. has correctly chosen Funkymonk's code as representing what he requested.
        My code addresses a different issue - sorting to the complete depth.

             "As you get older three things happen. The first is your memory goes, and I can't remember the other two... " - Sir Norman Wisdom

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Re^2: How would I sort a two-dimensional array by multiple columns?
by dbmathis (Scribe) on Mar 16, 2008 at 03:06 UTC

    How would I make this work if I am passing in @unsorted rather than $unsorted?

    After all this is over, all that will really have mattered is how we treated each other.
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      I had already indicated that in the comment of my previous node. Here it is again: 
      my @sorted =  sort NetWallahSort   @unsorted;

      [download]
      Note : I have updated "sub NetWallahSort" in the posted code, to include ikegami's suggestion, returning "0" instead of "1" when sort elements are equal. Please use a current copy of that code.

           "As you get older three things happen. The first is your memory goes, and I can't remember the other two... " - Sir Norman Wisdom

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        Sorry NetWallah, I was refering to Funk's code. I saw your previous comment, however your code appears to be sorting all depths and I need "sortRoutine(@array, 2, 1, 4, 5) for example.

        I have an existing piece of code that has an array of arrays that needs to be sorted like this and Funk's code was sorting an array of refs.


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Re^2: How would I sort a two-dimensional array by multiple columns?
by dbmathis (Scribe) on Mar 16, 2008 at 15:06 UTC

    Hi Funk, I like your solution and I am able to get it working fine in test, however in my existing code I will be passing a list of array references within an array to the routine (@unsorted).

    For example here's the part of my code where I am loading the array: 

    while ( @row = $sth->fetchrow_array ) {
    push @x, [ @row ];
}

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        $rindex = 0; $i = 1;
    do {
        foreach ( @columns ) {
            if ( $_ <= $qstart_column - 2 ) {
                $unsorted[$rindex][$_] = $x[$i][$_];
            } else {
                $unsorted[$rindex][$_] = $x[$i][$_ - $nun_of_questions
+];
            }
        }
        $rindex += 1; $i += $nun_of_questions;
    } while ( $i <= $#x );

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    Right now when run your code in my code I get the following: 

    Use of reference "ARRAY(0x10b5810)" as array index at /home/dmathis/qw
+est_qqs/transpose-qqs-dev line 367.
Use of reference "ARRAY(0x10b5810)" as array index at /home/dmathis/qw
+est_qqs/transpose-qqs-dev line 367.
Use of uninitialized value in numeric comparison (<=>) at /home/dmathi
+s/qwest_qqs/transpose-qqs-dev line 367.
Use of uninitialized value in numeric comparison (<=>) at /home/dmathi
+s/qwest_qqs/transpose-qqs-dev line 367.
................
................
................

    [download]

    I just need to figure out what to alter in your code to handle my array.

    Best Regards

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