Bioperl Training Exercise 4

1. create array

   my @id = qw/id2 id7 id1 id4 id3 id5 id6/;

2. add the following list of duplicates using an array function: id3 id2 id7 id2 id2 id3
3. Create a hash for which the keys are the unique elements in @id and values the number of occurences
4. Print the number of unique elements
5. Print the unique elements
6. Print the key/value pairs using the each function. Compare the order of the elements !
7. Print the key/value pairs again preserving the original order
8. Hash interpolation (= double quotes). What happens ?
9. Advanced: print the hash values in the same order as the original @id array using hash slice and interpolation
10. Advanced: print the top 3 of most occuring elements
11. Advanced: interpolate the keys of the hash (print the keys of the hash in double quoted string)

Solution

#!/usr/bin/perl use strict;   # create array (the keys that will be used in the hash) my @id = qw/id2 id7 id1 id4 id3 id5 id6/;   # add duplicates push @id, qw/id3 id2 id7 id2 id2 id3/;   # create hash: key => id, value => count # notice that you can use the same name ('''id''') as the array # no clash because other type my %id; $id{$_}++ for @id;   # number of unique elements in @id my $unique = keys %id; print "Number of unique elements: $unique\n"; # the unique elements themselves = keys of the hash my @unique = keys %id; print "Unique elements: @unique\n";     # Print the key/value pairs using the 'each' function print "key/value pairs:\n"; while (my ($key, $value) = each %id) { print "$key => $value\n"; }   # original keys array @id = qw/id2 id7 id1 id4 id3 id5 id6/;   # Print the key/value pairs again preserving the original order print "key/value pairs original order:\n"; foreach my $key (@id) { print "$key => $id{$key}\n"; }     # Hash interpolation (= double quotes). It does not work !! Only interpolation with @ and $ print "Interpolation of hash: %id\n";   # Advanced: print the hash values in the same order as the original @id array using hash slice and interpolation print "Interploation of hash slice (values): @id{@id}\n";   # Advanced: top 3 of most occuring elements my @most = (sort {$id{$b} <=> $id{$a}} @unique) [0..2]; print "Top 3: @most\n";   # Advanced: interpolate the keys of the hash print "Interploation of hash (keys): @{[keys %id]}\n";