Problems with array references in perl

Question

I am trying to count how many time DE10 and each of the keys in my ICD10 hash occurs in the same line in my file2.tsv. I further have to divide it by male/female (M/K). I therefore made a hash called results. Each of the keys in this is named after the key in the ICD10 hash, and they refers to an array of 2 elements, the first counting the male, the second counting the females.

But I get this warning:

Can't use string ("0") as an ARRAY ref while "strict refs"

due to this line:

  $results{$key}[1] +=1;

I am a little weak on this reference part, can someone help me with my mistake? thanks a lot

#!/usr/bin/perl -w
use strict;

###################
# loading my hash #
###################

my %icd10;

open(IN, '<', 'myfile.tsv') or die;
while (defined (my $line = <IN>)) {
chomp $line;
$icd10{$line} = 1;
}
close IN;

################
### COUNTING
#################

my %results;

open(IN, '<', 'myfile2.tsv') or die;
while (defined (my $line = <IN>)) {
chomp $line;
my @line = split('\t', $line);
my %hash;
for (my $i = 2; $i < scalar(@line); $i++){ 
    $hash{$line[$i]} = 1;
}

if (grep (m/^DE10/, keys %hash)) {
    foreach my $key (keys %icd10){
        if (grep (m/^$key/, keys %hash)) {
            if (exists $results{$key}) {
                if ($line[1] eq 'M') {
                    $results{$key}[1] +=1;
                }
                elsif ($line[1] eq 'K'){
                    $results{$key}[2] +=1;
                }
            }
            else{
                if ($line[1] eq 'M') {
                    $results{$key}=(1,0);
                }
                elsif ($line[1] eq 'K'){
                    $results{$key}=(0,1);
                }
            }

The parentheses in these two sentences $results{$key}=(1,0); and $results{$key}=(0,1); should be brackets, if you want $results{$key} to be a reference to an array. — Lee Duhem
– Lee Duhem, Commented Jan 18, 2014 at 10:08
Is this line a typo if (grep (m/^DE10, keys %hash)) { ? It should be if (grep (/^DE10/, keys %hash)) { — Toto
– Toto, Commented Jan 18, 2014 at 10:09
leeduhem: so it should be $results{$key}={1,0} ? It doesnt fix the problem — user2335015
– user2335015, Commented Jan 18, 2014 at 10:13

Lee Duhem · Accepted Answer · 2014-01-18 10:26:13Z

2

If you want $results{$key} to be a reference to an array, then the parentheses in these two identical sentences $results{$key}=(1,0); should be square brackets, like this: $results{$key}=[1,0];.

To create a reference to an array, you can use backslash operator:

$arrayref = \@array;

To create a reference to an anonymous array you should use square brackets:

$arrayref = [ 'ele1', 'ele2' ];

See perlref for further details.

edited Jan 18, 2014 at 10:26

answered Jan 18, 2014 at 10:17

Lee Duhem

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5 Comments

user2335015 Over a year ago

Okay, I might be really stupid , but Im not sure what I should change. if I write $results{$key}=[1,0]; I still have the same problem.

user2335015 Over a year ago

Im not sure what you mean by brackets

Lee Duhem Over a year ago

@user2335015 Change both $results{$key}=(1,0); to $results{$key}=[1,0]; does not work?

user2335015 Over a year ago

Arh sorry in my real code, there were a couple more places I need to change it. It seems to be running now. Thanks :)

Lee Duhem Over a year ago

@user2335015 Already changed 'brackets' to 'square brackets', I hope the meaning of this one is clear.

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