• DBI and DBD::CSV
• Text::CSV or Text::CSV::XS
• How do I shuffle an array randomly?
• It's Perl, not PERL.

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W5kIHBhY2soKS4gQnV0IGRvIHlvdS
ByZWNvZ25pc2UgQmFzZTY0IHdoZW4
geW91IHNlZSBpdD8gIC0tIEp1ZXJk

Good list, Juerd.

But you forgot "Make sure you have -w and use strict" :)
--
Mike

But you forgot "Make sure you have -w and use strict" :)

I assume every beginner already has seen that thousands of times. Besides, I'm convinced one has to experience strictless hell before enjoying strict - that's how I did it, and it made me love strict even more.

U28geW91IGNhbiBhbGwgcm90MTMgY
W5kIHBhY2soKS4gQnV0IGRvIHlvdS
ByZWNvZ25pc2UgQmFzZTY0IHdoZW4
geW91IHNlZSBpdD8gIC0tIEp1ZXJk

I saw the "How do I shuffle an array randomly?" but my concern with that is that it might randomize the words out of their original columns and not knowing enough about this I can't determine if that is the case.

HTH, --traveler

I tried the following on (a copy of) a csv dump of my last bank statement -- seems to do the job (could make taxes interesting this year...)

BTW, I suppose Fisher_Yates is good enough, but my own favorite has always been to prepend a random number to the string (default output of rand() is between 0.0 and 0.999...), then sort, then remove the random number.

use strict;
my @transpose;  # this will be an array of arrays
my $ncols = 0;

while (<>)
{
    chomp;
    my @cols = split(/,/);
    if ( $ncols ) {
        die "Line $. doesn't have $ncols columns\n"
            if ( $ncols != scalar @cols );
    } else {
        $ncols = scalar @cols;
    }
    foreach my $i (0..$#cols) {
        push( @{$transpose[$i]}, $cols[$i] );
    }
}
my $nrows = $.;
for (0..$ncols-1) 
{
    &fisher_yates_shuffle( $transpose[$_] );
}

foreach my $i (0..$nrows-1) {
    my @cols = ();
    foreach my $j (0..$ncols-1) {
        push( @cols, $transpose[$j][$i] );
    }
    print join( ",", @cols ) . "\n";
}
[download]

BTW, I suppose Fisher_Yates is good enough, but my own favorite has always been to prepend a random number to the string (default output of rand() is between 0.0 and 0.999...), then sort, then remove the random number.

Not only is it good enough, it's also a lot more efficient and scalable.

The Fisher_Yates algorithm is an inline sort, swapping array elements. Your solution first alters all elements, then sorts it, assigns the result of the sort to an array, after which you remove the string. I have not benchmarked it, but it sounds like a slow procedure - which may still be very useful for small arrays.



my @cols = split(/,/);

That's not CSV parsing. CSV isn't just comma-seperated, the format also supports quoted strings and escaping of quotes with other quotes. See Re (tilly) 1: csv output.

U28geW91IGNhbiBhbGwgcm90MTMgY
W5kIHBhY2soKS4gQnV0IGRvIHlvdS
ByZWNvZ25pc2UgQmFzZTY0IHdoZW4
geW91IHNlZSBpdD8gIC0tIEp1ZXJk

Thank you very much. That was very useful. Oh, frabjous day, Calloo, callay. :)