Adding a new element to an array in a hash of arrays

Question

I want to read and save the content of a file in a hash of array. The first column of each row would be the key. Then, I want to read the files in a directory and add the file name to the end of the array according to the key!

file ($file_info)

AANB    John    male
S00V    Sara    female
SBBA    Anna    female

files in the directory:

AANB.txt
SBBA.txt
S00V.txt

expected output:

AANB    John    male    AANB.txt
S00V    Sara    female  S00V.txt
SBBA    Anna    female  SBBA.txt

Here's the script itself:

#!/usr/bin/perl

use strict;
use warnings;

my %all_samples=();
my $file_info = $ARGV[0];

open(FH, "<$file_info");

while(<FH>) {
    chomp;
    my @line = split("\t| ", $_);

    push(@{$all_samples{$line[0]}}, $_);
}

my $dir = ".";
opendir(DIR, $dir);
my @files = grep(/\.txt$/,readdir(DIR));
closedir(DIR);

foreach my $file (@files) {
    foreach my $k (keys %all_samples){
        foreach my $element (@{ $all_samples{$k} }){
            my @element = split(' ', $element);
            if ($file =~ m/$element[0]/) {
                push @{$all_samples{$element}}, $file;
            }
            else {
                next;
            }
        }
    }

}

foreach my $k (keys %all_samples) {
    foreach my $element (@{ $all_samples{$k} }) {
        print $element,"\n";
    }
}

But the output is not what I expected

AANB    John    male
SBBA.txt1
S00V    Sara    female
SBBA    Anna    female
S00V.txt1
AANB.txt1

Answer 1

I think that

        my @element = split(' ', $element);
        if ($file =~ m/$element[0]/) {
            push @{$all_samples{$element}}, $file;
        }

Is not doing the right thing, so $all_samples{$element}} is a new arrayref. You're printing six one element arrays rather than three two element arrays.

But then it doesn't help that you're printing the array elements one per line.

I think that your final section should look more like this:

foreach my $k (keys %all_samples) {
    print join( "\t", @{ $all_samples{$k} } ) . "\n"
}

In general, I think that you're overcomplicating this script. Here's how I would write it:

#!/usr/bin/perl

use strict;
use warnings;

my $all_samples={};

while(<>) {
    chomp;
    # Note that I'm using variable names here to document
    # The format of the file being read. This makes for
    # easier trouble-shooting -- if a column is missing,
    # It's easier to tell that $file_base_name shouldn't be
    # 'Anna' than that $line[0] should not be 'Anna'.
    my ( $file_base_name, $given_name, $sex ) = split("\t", $_);
    push(@{$all_samples->{$file_base_name} }, ( $file_base_name, $given_name, $sex ) );
}

my $dir = ".";
opendir(DIR, $dir);
my @files = grep(/\.txt$/,readdir(DIR));
closedir(DIR);

FILE: foreach my $file (@files) {
    BASE: foreach my $base (keys %{$all_samples}){
        next BASE unless( $file =~ /$base/ );
        push @{$all_samples->{$base}}, $file;
    }
}

foreach my $k (keys %{$all_samples} ) {
    print join( "\t", @{ $all_samples->{$k} } ) . "\n";
}

I prefer hashrefs to hashes, simply because I tend to deal with nested data structures -- I'm simply more used to seeing $all_samples->{$k} than $all_samples{$k}... more importantly, I'm using the full power of the arrayref, meaning that I'm not having to re-split the array that's already been split once.

G. Cito brings up an interesting point: why did I use

push(@{$all_samples->{$file_base_name} }, ( $file_base_name, $given_name, $sex ) );

Rather than

push(@{$all_samples->{$file_base_name} }, [ $file_base_name, $given_name, $sex ] );

There's nothing syntactically wrong with the latter, but it wasn't what I was trying to accomplish:

Let's look at what $all_samples->{$base} would look like after

push @{$all_samples->{$base}}, $file;

If the original push had been this:

push(@{$all_samples->{$file_base_name} }, [ $file_base_name, $given_name, $sex ] );

@{$all_samples->{$base}} would look like this:

(
    [ $file_base_name, $given_name, $sex ],
    $file
)

If instead, we use

push(@{$all_samples->{$file_base_name} }, ( $file_base_name, $given_name, $sex ) );

@{$all_samples->{$base}} looks like this after push @{$all_samples->{$base}}, $file:

(
    $file_base_name, 
    $given_name, 
    $sex, 
    $file
)

For instance:

(
    "AANB",
    "John",   
    "male",    
    "AANB.txt"
)

So when we print the array:

print join( "\t", @{ $all_samples->{$k} } ) . "\n";

Will print

AANB    John    male    AANB.txt