Reading numbers from a file to variables (Perl) - perl

Question

I've been trying to write a program to read columns of text-formatted numbers into Perl variables.
Basically, I have a file with descriptions and numbers:
ref 5.25676 0.526231 6.325135
ref 1.76234 12.62341 9.1612345
etc.
I'd like to put the numbers into variables with different names, e.g.
ref_1_x=5.25676
ref_1_y=0.526231
etc.
Here's what I've got so far:
print "Loading file ...";
open (FILE, "somefile.txt");
#text=<FILE>;
close FILE;
print "Done!\n";
my $count=0;
foreach $line (#text){
#coord[$count]=split(/ +/, $line);
}
I'm trying to compare the positions written in the file to each other, so will need another loop after this.

Answer 1

Sorry, you weren't terribly clear on what you're trying to do and what "ref" refers to. If I misunderstood your problem please commend and clarify.
First of all, I would strongly recommend against using variable names to structure data (e.g. using $ref_1_x to store x coordinate for the first row with label "ref").
If you want to store x, y and z coordinates, you can do so as an array of 3 elements, pretty much like you did - the only difference is that you want to store an array reference (you can't store an array as a value in another array in Perl):
my ($first_column, #data) = split(/ +/, $line); # Remove first "ref" column
#coordinates[$count++] = \#data; # Store the reference to coordinate array
Then, to access the x coordinate for row 2, you do:
$coordinates[1]->[0]; # index 1 for row 2; then sub-index 0 for x coordinate.
If you insist on storing the 3 coordinates in named data structure, because sub-index 0 for x coordinate looks less readable - which is a valid concern in general but not really an issue with 3 columns - use a hash instead of array:
my ($first_column, #data) = split(/ +/, $line); # Remove first "ref" column
#coordinates[$count++] = { x => $data[0], y => $data[1], z => $data[2] };
# curly braces - {} - to store hash reference again
Then, to access the x coordinate for row 2, you do:
$coordinates[1]->{x}; # index 1 for row 2
Now, if you ALSO want to store the rows that have a first column value "ref" in a separate "ref"-labelled data structure, you can do that by wrapping the original #coordinates array into being a value in a hash with a key of "ref".
my ($label, #data) = split(/ +/, $line); # Save first "ref" label
$coordinates{$label} ||= []; # Assign an empty array ref
#if we did not create the array for a given label yet.
push #{ $coordinates{$label} }, { x => $data[0], y => $data[1], z => $data[2] };
# Since we don't want to bother counting per individual label,
# Simply push the coordinate hash at the end of appropriate array.
# Since coordinate array is stored as an array reference,
# we must dereference for push() to work using #{ MY_ARRAY_REF } syntax
Then, to access the x coordinate for row 2 for label "ref", you do:
$label = "ref";
$coordinates{$label}->[1]->{x}; # index 1 for row 2 for $label
Also, your original example code has a couple of outdated idioms that you may want to write in a better style (use 3-argument form of open(), check for errors on IO operations like open(); use of lexical filehandles; storing entire file in a big array instead of reading line by line).
Here's a slightly modified version:
use strict;
my %coordinates;
print "Loading file ...";
open (my $file, "<", "somefile.txt") || die "Can't read file somefile.txt: $!";
while (<$file>) {
chomp;
my ($label, #data) = split(/ +/); # Splitting $_ where while puts next line
$coordinates{$label} ||= []; # Assign empty array ref if not yet assigned
push #{ $coordinates{$label} }
, { x => $data[0], y => $data[1], z => $data[2] };
}
close($file);
print "Done!\n";
It is not clear what you want to compare to what, so can't advise on that without further clarifications.

Answer 2

The problem is you likely need a double-array (or hash or ...). Instead of this:
#coord[$count]=split(/ +/, $line);
Use:
#coord[$count++]=[split(/ +/, $line)];
Which puts the entire results of the split into a sub array. Thus,
print $coord[0][1];
should output "5.25676".