Read CSV file and save in 2 d array - arrays

Question

I am trying to read a huge CSV file in 2 D array, there must be a better way to split the line and save it in the 2 D array in one step :s
Cheers
my $j = 0;
while (<IN>)
{
chomp ;
my #cols=();
#cols = split(/,/);
shift(#cols) ; #to remove the first number which is a line header
for(my $i=0; $i<11; $i++)
{
$array[$i][$j] = $cols[$i];
}
$j++;
}

Answer 1

CSV is not trivial. Don't parse it yourself. Use a module like Text::CSV, which will do it correctly and fast.
use strict;
use warnings;
use Text::CSV;
my #data; # 2D array for CSV data
my $file = 'something.csv';
my $csv = Text::CSV->new;
open my $fh, '<', $file or die "Could not open $file: $!";
while( my $row = $csv->getline( $fh ) ) {
shift #$row; # throw away first value
push #data, $row;
}
That will get all your rows nicely in #data, without worrying about parsing CSV yourself.

Answer 2

If you ever find yourself reaching for the C-style for loop, then there's a good chance that your program design can be improved.
while (<IN>) {
chomp;
my #cols = split(/,/);
shift(#cols); #to remove the first number which is a line header
push #array, \#cols;
}
This assumes that you have a CSV file that can be processed with a simple split (i.e. the records contain no embedded commas).

Answer 3

Aside: You can simplify your code with:
my #cols = split /,/;
Your assignment to $array[$col][$row] uses an unusual subscript order; it complicates life.
With your column/row assignment order in the array, I don't think there's a simpler way to do it.
Alternative:
If you were to reverse the order of the subscripts in the array ($array[$row][$col]), you could think about using:
use strict;
use warnings;
my #array;
for (my $j = 0; <>; $j++) # For testing I used <> instead of <IN>
{
chomp;
$array[$j] = [ split /,/ ];
shift #{$array[$j]}; # Remove the line label
}
for (my $i = 0; $i < scalar(#array); $i++)
{
for (my $j = 0; $j < scalar(#{$array[$i]}); $j++)
{
print "array[$i,$j] = $array[$i][$j]\n";
}
}
Sample Data
label1,1,2,3
label2,3,2,1
label3,2,3,1
Sample Output
array[0,0] = 1
array[0,1] = 2
array[0,2] = 3
array[1,0] = 3
array[1,1] = 2
array[1,2] = 1
array[2,0] = 2
array[2,1] = 3
array[2,2] = 1