Re: creating adjacency matrix

You are asking for basically an "and" table. There are a bunch of ways that this could be made faster. But this is a fairly straight-forward general solution that does what you asked for.
I did test this expanding to A-E and testing "C E" as a pair.

that printed:
  A B C D E
A 0 1 0 0 0
B 1 0 1 0 0
C 0 1 0 1 1
D 0 0 1 0 0
E 0 0 1 0 0
[download]

#!/usr/bin/perl -w
use strict;
use Data::Dumper;

=this prints
  A B C D
A 0 1 0 0
B 1 0 1 0
C 0 1 0 1
D 0 0 1 0
=cut

my @vars = qw(A B C D);
my @square_matrix = map{ my @x;
                         push (@x,0) foreach @vars;
                         [@x]
                       }@vars;
my $num =0;
my %ltr2num = map{ $_ => $num++ }@vars;

my @pairs = ("A B", "B C", "C D"); ### the user input ####

foreach my $pair (@pairs)
{
   my ($x, $y) = split ' ',$pair;
   enter_pair_in_matrix ( $ltr2num{$x},
                          $ltr2num{$y},
                          \@square_matrix
                         );
}

dump_square_matrix(\@vars,\@square_matrix);

sub enter_pair_in_matrix
{
   my ($x,$y,$ref_matrix) = @_;
   $ref_matrix->[$x][$y]= 1;
   $ref_matrix->[$y][$x]= 1;
}

sub dump_square_matrix
{
   my ($ref_vars, $ref_matrix) = @_;
   
   my @vars = @$ref_vars;
   print "  ","@vars\n";
   
   foreach (@$ref_matrix)
   {
      print shift @vars, " @$_\n";
   }
}
[download]

Comment on Re: creating adjacency matrix Select or Download Code

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Re^2: creating adjacency matrix by ramdat (Initiate) on Jan 11, 2011 at 04:51 UTC
Thank you very much..It worked for me.Likewise i understood @square_matrix returns address values and But I am not able understand the squarebraces of @x use in the map function..Would be thankful to your answer..	[reply]
Re^3: creating adjacency matrix by Marshall (Canon) on Jan 11, 2011 at 09:31 UTC
The matrix is represented as an array of arrays. Add a `use Data::Dumper;` statement, then various `print Dumper \@square_matrix;` statements to see how the data is being represented. `example of a 3x3: my @m = ([0,0,0], [0,0,0], [0,0,0]);` [download] Each "row" is what the [@x] represents and is the return value of the map. Another set of code in this thread uses a hash table to represent the data. The main idea is to make a square matrix and then each set of letters results in two entries into that matrix. Many implementations of that idea are possible, some much shorter than what I did in this case. Update: This might help you to understand what is going on without a map...a map is kind of like a "tricky" foreach() loop. `#!/usr/bin/perl -w use strict; use Data::Dumper; my @sq_matrix_3x3; my @list = (1,2,3); foreach (@list) { push (@sq_matrix_3x3, [0,0,0]); #creates a row with 3 elements } print "3x3 Matrix: "; print Dumper \@sq_matrix_3x3;` [download] This is the same thing and perhaps a more familiar form of `[x][y]` coordinates `my @another_2D; for (my $x=0; $x<3; $x++) { for (my $y=0; $y<3; $y++) { $another_2D[$x][$y]=0; } } print Dumper \@another_2D; __END__ prints: 3x3: $VAR1 = [ [ 0, 0, 0 ], [ 0, 0, 0 ], [ 0, 0, 0 ] ]; # print Dumper \@sq_matrix_3x3; #these both produce the same output # print Dumper \@another_2D;` [download]	[reply] [d/l] [select]