my $id;   # ??
foreach my $window ( @{ $data{$id} } ) {

  # only pass windows with > min number of stats (i.e. >1 for now), an
+d
  # of course we also ignore any 'undef' windows.
  next unless scalar @{ $data{$id} }[$window] >= 2;

    foreach my $individual ( keys(%data) ) {