Sorting an array in perl

Question

I have an array in perl that contains about 200 indexes that are for a csv file. It likes like the lines below:

46.9234784633993,Springwood Drive,Naples,FL
89.7786182217159,W 8th St,Lakeland,FL

I want to sort them by that number before the first comma. I tried using just sort, but sometimes the numbers get into the hundreds and thousands and it just sorts all those in the 1's. Then a numerical sort doesnt like it since they are not numerical entries

I tried this

my @sortedDistances = sort{ $a <=> $b }(@completedDistances);
and
my @sortedDistances = sort(@completedDistances);

Then a numerical sort doesn't like it since they are not numerical entries ???? — user1972382
– user1972382, Commented Jan 18, 2013 at 22:04
Show us what you have tried. We can't tell from your description what you have done wrong. Edit your question to include the failing code. Then, describe what exactly is not working. What happened when you tried it? Did you get incorrect results? Did you get no results? If the results were incorrect, what made them incorrect? What were you expecting instead? Did you get any correct results? If so, what were they? Don't make us guess. — Andy Lester
– Andy Lester, Commented Jan 18, 2013 at 22:11

Borodin · Accepted Answer · 2013-01-19 01:36:11Z

5

This is a possible solution, try if it works:

open FILE, "<", $ARGV[0] or die $!;
my @sorted =
    map { join ",", @{$_} }
    sort { $a->[0] <=> $b->[0] }
    map { [ split /,/ ] } <FILE>;
close FILE;
say join "\n", @sorted;

EDIT: changed colon to comma

edited Jan 19, 2013 at 1:36

Borodin

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answered Jan 18, 2013 at 22:22

user1972382

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1 Comment

amon Over a year ago

This is actually the correct answer. It might be worth noting that using something like split /,/, $_, 2 (with third argument) is more efficient, as it limits the number of regex matches performed. (Also, chomping and then joining with a newline is hilarious; print @sorted should work as well)

Borodin · Accepted Answer · 2013-01-19 01:49:52Z

4

The classic Schwartzian Transform, which I think @sdir intended to code, would look like this

use strict;
use warnings;

my @sorted =  map $_->[0],
              sort { $a->[1] <=> $b->[1] }
              map [$_, /([^,]+)/], <>;

print for @sorted;

answered Jan 19, 2013 at 1:49

Borodin

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1 Comment

Kenosis Over a year ago

If the last unsorted csv line doesn't end with \n and that line is not the last after the sort, two lines will print together, e.g., "46.9234784633993,Springwood Drive,Naples,FL89.7786182217159,W 8th St,Lakeland,FL". Perhaps map {chomp; [$_, /([^,]+)/]} <>; and then print join "\n", @sorted; would help.

pulven · Accepted Answer · 2013-01-18 22:14:51Z

1

normal sort to the rescue

sort -t, -n -k1,1 file.cvs

-t, means separate at comman

-n or -g numerical sort

-k1,2 use column 1 to 2 see -t

man sort

answered Jan 18, 2013 at 22:14

pulven

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3 Comments

pulven Over a year ago

@sdir: no, but the pure guy mentioned 'sort' him self, and used right it can save you a lot of time writing funny perl oneliners, - and debugging them.

user1972382 Over a year ago

True that. I definitely would have done it with shell sort, too. But perl is more fun (and I use that 'oneliner' actually alot). No offense itended btw.

shinjuo Over a year ago

Sorry it would have worked but I need to keep it perl now. I didn't know this needs to be done automatically 35000 times

Glenn · Accepted Answer · 2013-01-18 22:20:18Z

-1

I would write a sort function to get the first item from each and then do the comparison on the items. It would be of the form:

sub sortStuff($$)
{
  my ($a) = split(',',$_[0]);
  my ($b) = split(',',$_[1]);

  return ( $a <=> $b ) ;
}

and then call the subroutine as part of the call to sort:

@sortedArray = sort sortStuff @array;

It will sort on the number and ignore the rest of the items on the line.

answered Jan 18, 2013 at 22:20

Glenn

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