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One way to do this is to transform the hash structure into an AoA so that it is easier to sort, then take first (index 0) and last (index -1) to get min and max. This type of approach allows easy reporting "ties" for min or max if that is important to you, eg maybe the minimum occurs on three different dates. Perl is very good at sorting and this runs faster than one might imagine.

#!/usr/bin/perl -w use strict; use Data::Dumper; my %years =( 2007 => { '01' => 07, '02' => 34, '10' => 24, '09' => 14, }, 2008 => { '01' => 11, '02' => 64, '03' => 20, '09' => 13, }, ); my @year_data; foreach my $year (keys (%years)) { foreach my $month (keys %{$years{$year}}) { push (@year_data, [$year, $month, $years{$year}{$month}]); } } @year_data = sort { my ($yearA, $monthA, $dataA) = @$a; my ($yearB, $monthB, $dataB) = @$b; $dataA <=> $dataB or $monthA <=> $monthB or $yearA <=> $yearB }@year_data; print "minimum is: @{$year_data[0]}\n"; print "maximum is: @{$year_data[-1]}\n"; #minimum is: 2007 01 7 #maximum is: 2008 02 64

In reply to Re: min and max in a hash of hash by Marshall
in thread min and max in a hash of hash by nagalenoj

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    [GrandFather]: I haven't any "working code" to inspect! I have to find ways to generate reference signals then check the numbers I get at the far end match.
    [GrandFather]: That's ok when the signal is a voltage, but there are three axis accelerometers, gyroscopes and magnetometers in these things! A little invention is needed at times!
    [Corion]: GrandFather: Yeah, in that aspect, hardware is far more a black box than software
    [GrandFather]: Oh, and the manufacturer tells lies too! I'm sure they don't mean to, but I know for sure some of the stuff they say is just wrong. It's possible they don't understand what we are asking, but that's not a good look either
    [Corion]: GrandFather: Ah, unit testing hardware is fun, especially when the hardware is uncalibrated ...
    [GrandFather]: Us: "What scaling do we need to apply to the numbers from the SDK for the wibble?". Them: "Oh, the numbers from the SDK for the wibble are already correct, they don't need scaling"
    [GrandFather]: In our code: wibble range 1 scale by 1, range 2 scale by 2, range 3 scale by 4, range 4 scale by 8

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