CODEWITHSUNDEEP
perlmultidimensional-arrayslice
Amelio Vazquez-Reina
Amelio Vazquez-Reina

Reputation: 96274

Collecting subarrays from multidimensional arrays in Perl

Say I build the following multidimensional array:

my @array;  # don't need the empty list
my @other_array = (0 ... 10);

foreach my $i ( 0 .. 10 ) {
$array[$i] = [ @other_array[1..$#other_array] ];
}

I would like to collect a "column" of this multidimensional array into a separate array,

For example, if I want to collect the items in the first column, I would like something like

my @other_array = ();
@other_array = $array[:][1]; # This does NOT work in Perl

Is there a way to do this in Perl without looping?

Eventually what I want to do is get the array of max of each column of my multidimensional array.

PS: This question is inspired by this other question: Building and printing a multidimensional list in Perl without looping.

Upvotes: 1

Views: 2858

Answers (3)

snoofkin
snoofkin

Reputation: 8895

For your example, this might be an overkill solution, but assuming your are planing to do this with huge multi-dimensional arrays (matrix's), use PDL and do a transpose then slice out the desired line.

Upvotes: 2

Zaid
Zaid

Reputation: 37146

Befriend map:

my @other_array = map $array[$_][1], 0 .. $#array;

The Slices section in perldoc perllol has more examples.

Upvotes: 4

zostay
zostay

Reputation: 3995

I think you want:

my @other_array = map { $_->[1] } @array;

Another language might have a special syntax for this operation, but it would still be performing a loop under the hood.

Upvotes: 5

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