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You would need to detail the correlation algorithm you want to use. The simple one I tried was this where $v would be either 'price' or 'qu'. This assumes for any date you have the full data, so you need to decide how to handle the dates where you don't have 2 prices or qu to correlate.

sub correlate { my ($p1,$p2,$v) = @_; return if $p1 eq $p2; my ($xy,$x2,$y2); for my $date (sort keys %data){ my $x = $data{$date}{$p1}{$v} - $total{$p1}{$v}{'mean'} ; my $y = $data{$date}{$p2}{$v} - $total{$p2}{$v}{'mean'} ; $xy += $x * $y; $x2 += $x * $x; $y2 += $y * $y; } my $cor = $xy / sqrt($x2 * $y2); print "$p1 $p2 $v $cor\n"; }

Update - after seeing Re^2: creating and managing many hashes

#!/usr/bin/perl use strict; use warnings; my $infile = 'products.txt'; my %data = (); my %total = (); my $records = 0; my $t0 = time(); open IN,'<',$infile or die "Could not open $infile $!"; while (<IN>){ my ($date, $product, $price, $qu) = split /\s+/,$_; $data{$date}{$product}{'price'} = $price; $data{$date}{$product}{'qu'} = $qu; $total{$product}{'count'} += 1; $total{$product}{'price'}{'sum'} += $price; $total{$product}{'qu'}{'sum'} += $qu; ++$records; } close IN; # calculate stats my $outfile = 'report.txt'; open OUT,'>',$outfile or die "Could not open $outfile"; for my $prod (keys %total){ my $count = $total{$prod}{'count'}; # mean $total{$prod}{'price'}{'mean'} = $total{$prod}{'price'}{'sum'}/$coun +t; $total{$prod}{'qu'}{'mean'} = $total{$prod}{'qu'}{'sum'}/$count; # std dev squared my ($sum_x2,$sum_y2); for my $date (keys %data){ my $x = $data{$date}{$prod}{'price'} - $total{$prod}{'price'}{'mea +n'}; $sum_x2 += ($x*$x); my $y = $data{$date}{$prod}{'qu'} - $total{$prod}{'qu'}{'mean'}; $sum_y2 += ($y*$y); } $total{$prod}{'price'}{'stddev'} = sqrt($sum_x2/$count); $total{$prod}{'qu'}{'stddev'} = sqrt($sum_y2/$count); my $line = join "\t",$prod, $total{$prod}{'price'}{'mean'}, $total{$prod}{'price'}{'stddev'}, $total{$prod}{'qu'}{'mean'}, $total{$prod}{'qu'}{'stddev'}; print OUT $line."\n"; } close OUT; # correlate first 5 products against the rest $t0 = time; for (1..5){ my $p1 = sprintf 'product_%04d',$_; print "Correlating $p1\n"; open OUT,'>',"correlate_${p1}.txt" or die "$!"; for my $p2 (sort keys %total){ correlate($p1,$p2,'price'); } close OUT; } # summary my $dur = time - $t0; printf " Products : %d Dates : %d Records : %d Run Time : %d s",0+keys %total, 0+keys %data, $records, $dur; sub correlate { my ($p1,$p2,$v) = @_; return if $p1 eq $p2; my $sigma; my $count = 0; for my $date (sort keys %data){ # skip missing dataset next unless (defined $data{$date}{$p1} && defined $data{$date}{$p2 +}); my $zee1 = ( $data{$date}{$p1}{$v} - $total{$p1}{$v}{'mean'} ) / $ +total{$p1}{$v}{'stddev'} ; my $zee2 = ( $data{$date}{$p2}{$v} - $total{$p2}{$v}{'mean'} ) / $ +total{$p2}{$v}{'stddev'} ; $sigma += ( $zee1 * $zee2 ); ++$count; } my $cor = $sigma / ( $count - 1 ) ; print OUT "$p1 $p2 $v $cor\n"; }

In reply to Re^5: creating and managing many hashes by poj
in thread creating and managing many hashes by Gtforce

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