In that case, I think you need two data structures. Here's some half-baked code. 

while ( defined( my $record = <$input_fh> ) ) {
    my %record_hash = rec2hash( $record );
    while ( my ( $field, $value ) = each %record_hash ) {
        my $variant = variant_of( $value );
        $variants_in{ $record }{ $field }{ $variant } = 1;
        push @{ $records_for{ $field }{ $variant } }, $record;
    }
}

[download]

Here I store for each field-variant pair, every record that has that pair. Also for each record, I have every variant that's present in it. I leave it to you to take a record and turn it into field-value pairs, and I also leave it to you to turn a particular value into a "variant" (each value may be. a variant, but I can't tell from your description).

From here you figure out which field-variant pair you want to represent most by looping through the pairs in %records_for and finding which pair has the fewest records available. From that you get a list of records which exemplify that field-variant pair.

Then look in %variants_in for each record and see which one represents the most different field-variant pairs. That will be one of your examples.

Then you can delete that record from %variants_in, and you'll want to take every field-variant pair in that record and delete them from %records_for since you no longer need examples of them.

Then go back and pick another record of interest until there aren't any more.

Instead of a multi-level hash, it may make it easier to pick some separator and store field-variant pairs that way. That is, you do $records_for{ "$field$separator$variant" } instead of $records_for{ $field }{ $variant }. The problem with this is you have to make sure the separator never appears in your fields or variants.

Hope this helps.

In reply to Re^3: Most efficient record selection method? by kyle
in thread Most efficient record selection method? by Kraythorne

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.