Normalise numbers

Normalise a list of numbers to the range 0 - 1

Update to fix $min == $max bug

use strict;
use warnings;
use List::MoreUtils qw(minmax);

my @numbers = (23, 4, -6.5, 10.7, 123, 99.5);

my ($min, $max) = minmax (@numbers);
my $scale = 1.0 / ($max == $min ? $max : $max - $min);
@numbers = map {($_ - $min) * $scale} @numbers;

print join ", ", @numbers;
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Re: Normalise numbers by merlyn (Sage) on Nov 04, 2005 at 08:55 UTC
If $max = $min, shouldn't you scale all the numbers to 1? So scale should be set to either $max or $min. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re^2: Normalise numbers by GrandFather (Saint) on Nov 04, 2005 at 21:46 UTC
You spotted the bug, but not the solution. You can't "scale" 0 to 1, you have to offset it. To handle that you would need to add another test to the code and adjust $min in the $min == $max special case: `$min -= 1 if $min == $max;` [download] You can however offset anything to 0, so the bug fix has that result. Perl is Huffman encoded by design.	[reply] [d/l]