in reply to Re^4: regular expessions question: (replacing words)
in thread regular expessions question: (replacing words)

Does your data fit into memory? If not, it gets more complicated (or you just have to wait a long time for the data file to get read dozens of times). You would either have to store it into a database or compress it (i.e. 'z' is 1, not-z is 0, so that every element uses just one bit)

If yes, read the file into an Array of Arrays:

my @data; 
my $n=0;
while ($organized=<DATA2>) {
  chomp;
  $organized=~s/(\s)\w+/$1z/g;
  push @{$data[$n++]}, (split /\s+/, $organized);
}

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Now accessing column 5 of line 2 is just a simple $data[2][5]

Now to get it easier, split your problem into easier parts. Create a subroutine that gets as parameter an arbitrary number of columns. This subroutine just counts all rows that have a 'z' in all these columns. You can do that with a loop (over the selected columns) inside a loop (over all rows).

If you got that working (test it with some simple data), just create another array, add a random number. Then repeatedly add a random number (that is not already in the array) to the array, call the subroutine with it. Do that 18 times.

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Re^6: regular expessions question: (replacing words)
by $new_guy (Acolyte) on Sep 28, 2010 at 07:28 UTC
    Hi Jethro,

    Thanks for the explanation!

    Yes the data fits in memory! And yes it would be appropriate to say every z is 1 and non-z is 0.

    I still don't understand! How do I select two columns at random, then count only the z's that are common to all rows in the two columns. By count I meant if a z occurs in column 1 at row 6 and column 2 at row six then my count of z's would be 1. Notice my count will increase as I go down comparing the rows.

    Thanks
[reply]

      That with the 0 and 1 would only have been necessary if you needed to compress the data , i.e. save memory. Which you say isn't the case.

      Ok, here is the subroutine that counts rows with all 'z' in specific columns:

      sub countrows {
# First parameter is a pointer/reference to the data
# Second parameter is an array of columns numbers
  my ($data,@f)= @_;
  my $count=0;
  foreach my $row (@$data) {
    my $success=1;
    foreach (@f) {
      if ($row->[$_] ne 'z') {
        $success=0;
        last;
      }
    }
    $count+= $success;
  }
  return $count;
}

my @data= ( ['z',4,'z',4,'z'],['z',4,'z',4,4],['z','z','z',4,'z'] );

print countrows(\@data,0,2),' ',countrows(\@data,1,3,2),' ',countrows(
+\@data,4),"\n";

# print 3 0 2

      [download]

      Now to get an array of random numbers. To make sure I don't get numbers twice I generate an array of all numbers up to the number of columns and pick (i.e. extract and delete) random numbers from that array

      sub randomarray {
  my ($columns,$count)= @_;
  my @all;
  push @all, $_ foreach (0..($columns-1));
  my @randarray;
  while ($count-- >0) {
    push @randarray, splice(@all, int(rand(@all)),1);
  }
  return @randarray;
}

print join ' ',randomarray( scalar @{$data[0]} , 2 ),"\n";
print join ' ',randomarray( scalar @{$data[0]} , 3 ),"\n";
print join ' ',randomarray( scalar @{$data[0]} , 4 ),"\n";

# might print  
3 4 
3 0 1 
0 1 4 2

      [download]

      You see how I cut the problem into smaller pieces that are easier to tackle? Ok, the subroutines are still not trivial. But you should be able to connect them in a sensible way to solve your problem

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