#!/usr/local/bin/perl
# sim.pl
=head1 NOTES
This script is the basic simulator with graphical output. This is just a toy implementation
designed to run a single simulation to give the user a feel for what is going on.
As with all the scripts, Perl must be installed.
For this script alone, (but none of the others) the Tk library must also be in the lib.
On Linux (or similar) you'll need to get Tk from CPAN (www.cpan.org) and install it yourself.
On Windows, the best option is to get a recent version of ActivePerl (www.activestate.com), which
is free, and has all the Tk libraries ready to go.
The usage is:
perl -w sim.pl
Defaults will give the maximum cultural isolation, as in the paper.
What you'll see is a 3-panelled screen with the population in each cell in the top,
the frequencies of gene 1 perl cell in the middle
and the frequencies of meme A per cell in the lower panel.
To see a rather different effect, try:
perl -w sim.pl -contag 0.49 -nn_contag 0.6 -cultsel Y -natsel Y
Those parameters should cause fairly rapid spread of meme A to fixation
If you want the simulation to run for longer try:
perl -w sim.pl -time 200
Other things can be changed by rewriting the script, like:
$popsize : the initial population size (default 200)
$rep_rate : the reproduction rate (default 1%)
$capacity : the max. population capacity per cell (default quasi-infinite)
$pause : the refresh rate of the graphical display (default 1 ie. every cycle)
As with all Perl scripts, they are offered as is, without any warranties concerning
safety, functionality etc
The author welcomes any comments on any aspects of the software.
to: dgatherer2002@yahoo.co.uk
This is an occasionally on-going project and newer versions of code are frequently
available, so if you want the really rough cuts, please ask.
=cut
#------PRELIMINARIES-------------------------------------------------#
use strict; # the Holy Trinity of Perl pragmas/modules
use POSIX;
eval { use Tk; };
srand(); # initialise randomiser
#------VARIABLES-----------------------------------------------------#
my $popsize = 400; # initial pop
my $time = 1000; # over gens
my $line = my $cols = 10; # in a 10 by 10 landscape
my $rep_rate = 0.01; # pop grows per generation
my $contag_rate = 0; # population contage to neighbour per gen
my $nn_contag_rate = 0; # chance of contag to other culture
my $mig_rate = 0; # pop move every gen
my $capacity = 100000000; # max pop per cell
my @pop; # map of pop density
my @trait_state;
my @gene_state;
my $pause = 1; # when to stop and draw the map
my $cult_sel = "N"; # no cultural selection
my $nat_sel = "N"; # no natural selection (of trait)
foreach(@ARGV)
{
if(/-help/)
{
die "\nUsage: perl -w Listing1.pl -num -time -size -cultsel -natsel\n";
}
}
my %args = @ARGV;
if(exists($args{-num})) {$popsize = $args{-num}; print "\npopsize\t$popsize";}
if(exists($args{-time})) {$time = $args{-time}; print "\ntime\t$time";}
if(exists($args{-cultsel})) {$cult_sel = $args{-cultsel}; print "\ncult. sel.\t$cult_sel";}
if(exists($args{-natsel})) {$nat_sel = $args{-natsel}; print "\nnat. sel.\t$nat_sel";}
if(exists($args{-contag})) {$contag_rate = $args{-contag}; print "\ncontag.\t$contag_rate";}
if(exists($args{-nn_contag})) {$nn_contag_rate = $args{-nn_contag}; print "\nnn_contag.\t$nn_contag_rate";}
if(exists($args{-migrate})) {$mig_rate = $args{-migrate}; print "\nmigrate\t$mig_rate";}
foreach($popsize, $time)
{
if(/[\D+]/)
{
die "\npopulation size, time must all positive integers\n";
}
}
foreach($cult_sel, $nat_sel)
{
unless(/[YN]/)
{
die "\nCultSel and NatSel must be just Y or N\n";
}
}
foreach($contag_rate, $nn_contag_rate, $mig_rate)
{
unless($_ =~ /[\d\.-]/ && ($_ <= 1) && ($_ >= 0))
{
die "\ncontagion rates and migration rate must be between 0 and 1\n";
}
}
#------GRAPHIC_OUTPUT-----------------------------------------------------#

my $top = MainWindow->new();
$top->title ("inter:$nn_contag_rate intra:$contag_rate mig:$mig_rate");
my $title = $top->Label(text => "gen.", anchor => "c", relief => "raised", width => 50, height => 1) -> pack();
my $pop_title = $top->Label(text => "population", anchor => "c", relief => "raised", width => 50, height => 1) -> pack();
my $pop_top = $top->Label(relief => "raised", width => 50, height => 11) -> pack();
my $gene_title = $top->Label(text => "vertical", anchor => "c", relief => "raised", width => 50, height => 1) -> pack();
my $gene_top = $top->Label(relief => "raised", width => 50, height => 11) -> pack();
my $trait_title = $top->Label(text => "horizontal", anchor => "c", relief => "raised", width => 50, height => 1) -> pack();
my $trait_top = $top->Label(relief => "raised", width => 50, height => 11) -> pack();
my @pop_buts; # AoAs of buttons, and co-ords
my @gene_buts;
my @trait_buts;
my @xpos;
my @ypos;
for(my $x=0; $x<=$line-1; $x++)
{
for(my $y=0; $y<=$cols-1; $y++)
{
$pop[$x][$y] = 0;
$trait_state[$x][$y] = sprintf("%.2f", 0);
$gene_state[$x][$y] = sprintf("%.2f", 0);
$xpos[$x][$y] = ($x%$line) * 1/$line;
$ypos[$x][$y] = ($y%$cols) * 1/$cols;
$pop_buts[$x][$y] = $pop_top->Button(-text => $pop[$x][$y], -anchor => 'c', -relief => "flat", -background => "yellow") -> pack();
$pop_buts[$x][$y]->place(-relx => $xpos[$x][$y], -rely => $ypos[$x][$y], -relwidth => 1/$cols, -relheight => 1/$line);
$gene_buts[$x][$y] = $gene_top->Button(-text => $gene_state[$x][$y], -anchor => 'c', -relief => "flat", -backgrounnd => "yellow") -> pack();
$gene_buts[$x][$y]->place(-relx => $xpos[$x][$y], -rely => $ypos[$x][$y], -relwidth => 1/$cols, -relheight => 1/$line);
$trait_buts[$x][$y] = $trait_top->Button(-text => $trait_state[$x][$y], -anchor => 'c', -relief => "flat", -backgrounnd => "yellow") -> pack();
$trait_buts[$x][$y]->place(-relx => $xpos[$x][$y], -rely => $ypos[$x][$y], -relwidth => 1/$cols, -relheight => 1/$line);
}
}
#------MAIN CODE SEQUENCE---------------------------------------------#
my $pop = &evenly_initialise();
&pop_state($pop); # look at it
for(my $gen=1;$gen<=$time;$gen++) # for a certain number of cycles
{
$title->configure(text => "gen. $gen");
$title->update;
$pop_title->configure(text => "population $popsize");
$pop_title->update;
$pop = &reproduce($pop); # replicate and pass traits by contagion
$pop = &migrate($pop); # move strings over grid
if($gen%$pause ==0) # can speed by having $pause > 1
{
&pop_state($pop);
} # look at it
}
MainLoop();
#-----SUBROUTINES-----------------------------------------------------#
#----------------------------------------------------------------------
sub pop_state() # prints current pop
{
my $input = $_[0];
my $av_fitness = $input ->{FITNESS};
my @current_pop = @{ $input ->{POPULATION} };
>
my @gene_state; # arrays for calculating the
my @trait_state; # horizontal and vertical dispersal
for(my $x=0; $x<=$line-1; $x++)
{
for(my $y=0; $y<=$cols-1; $y++)
{
my $freq_A = my $freq_1 = 0;
my $cell_count = 0; # how many per cell
foreach(@current_pop)
{
my $xcoord = $_ -> { LOCATION }[0];
my $ycoord = $_ -> { LOCATION }[1];
if($xcoord == $x && $ycoord == $y)
{
$cell_count++;
if($_ -> { TRAIT } eq "A")
{
$freq_A++;
}
if($_ -> { SERIAL_NUM } == 1)
{
$freq_1++;
}
}
}
$pop[$x][$y] = $cell_count;
if($freq_A == 0 && $freq_1 == 0 && $pop[$x][$y] == 0)
{
$trait_state[$x][$y] = 0;
$gene_state[$x][$y] = 0;
}
else
{
$freq_A /= $pop[$x][$y];
$freq_1 /= $pop[$x][$y];
$pop_buts[$x][$y]->configure(-text => $pop[$x][$y]);
$pop_buts[$x][$y]->update;
$trait_state[$x][$y] = sprintf("%.2f", $freq_A);
$trait_buts[$x][$y]->configure(-text => $trait_state[$x][$y]);
if($trait_state[$x][$y] > 0 && $trait_state[$x][$y] < 0.5)
{
$trait_buts[$x][$y]->configure(-background => "green");
}
elsif($trait_state[$x][$y] >= 0.5)
{
$trait_buts[$x][$y]->configure(-background => "red");
}
else{ $trait_buts[$x][$y]->configure(-background => "yellow"); }
$trait_buts[$x][$y]->update;
$gene_state[$x][$y] = sprintf("%.2f", $freq_1);
$gene_buts[$x][$y]->configure(-text => $gene_state[$x][$y]);
if($gene_state[$x][$y] > 0 && $gene_state[$x][$y] < 0.5)
{
$gene_buts[$x][$y]->configure(-background => "green");
}
elsif($gene_state[$x][$y] >= 0.5)
{
$gene_buts[$x][$y]->configure(-background => "red");
}
else{ $gene_buts[$x][$y]->configure(-background => "yellow"); }
$gene_buts[$x][$y]->update;
}
}
}
# &disp_calc(\@gene_state, \@trait_state); # try this if you want - write your own output code inside the sub (see below)
}
#--------------------------------------------------------------------
sub reproduce()
{
my $input = $_[0];
my $contag_events = my $repro_events = 0; # how many per cycles
for(my $b=0;$b<=$popsize-1;$b++) # run through pop
{
my $rand = rand();
if($nat_sel =~ /Y/i && @{ $input ->{POPULATION} }[$b] ->{TRAIT} eq "A")
{
$rand /= 2; # double the random number
}
if($rand < $rep_rate) # also duplicate every 10th one
{
my $xcoord = @{ $input ->{POPULATION} }[$b] -> { LOCATION }[0];
my $ycoord = @{ $input ->{POPULATION} }[$b] -> { LOCATION }}[1];
if($pop[$xcoord][$ycoord] < $capacity)
{
my @new_one_seq;
my $new_seq =
{
LOCATION => [ $xcoord, $ycoord ],
SERIAL_NUM => @{ $input ->{POPULATION} }[$b] ->{SERIAL_NUM},
TRAIT => @{ $input ->{POPULATION} }[$b] ->{TRAIT},
};
@{ $input ->{POPULATION} }[$popsize++] = $new_seqq;
$pop[$xcoord][$ycoord]++;
$repro_events++;
}
}
$rand = rand();
if($cult_sel =~ /Y/i && @{ $input ->{POPULATION} }[$b] ->{TRAIT} eq "A")
{
$rand *= 2; # halve the random number
}
if($rand < $contag_rate) # and contage every 10th one
{
my $chosen_one = floor($rand*$popsize);
while(abs(@{ $input ->{POPULATION} }[$b] -> { LOCATION }}[0]
- @{ $input ->{POPULATION} }[$chosen_one] ->{ LOOCATION }[0]) > 1
|| abs(@{ $input ->{POPULATION} }[$b] -> { LOCATION }[1]
- @{ $input ->{POPULATION} }[$chosen_one] -> { LOCATION }[1]) > 1)<
{ # replace with random other string
my $chos_rand = rand();
$chosen_one = floor($chos_rand*$popsize);
}
if($rand < $nn_contag_rate)
{
if(abs(@{ $input ->{POPULATION} }[$b] -> { LOCATION }}[0]
- @{ $input ->{POPULATION} }[$chosen_one] ->{ LOOCATION }[0]) <= 1
&& abs(@{ $input ->{POPULATION} }[$b] -> { LOCATION }[1]
- @{ $input ->{POPULATION} }[$chosen_one] -> { LOCATION }[1]) <= 1)
{
@{ $input ->{POPULATION} }[$b] ->{TRAIT} = @{ $input ->{POPULATION} }[$chosen_one] ->{TRAIT};
my $xcoord = @{ $input ->{POPULATION} }[$b] -> { LOCATION }[0]; # direct access, better ??
my $ycoord = @{ $input ->{POPULATION} }[$b] -> { LOCATION }[1]; # yes, same method for string access
my $trait = @{ $input ->{POPULATION} }[$b] -> { TRAIT };
$contag_events++;
next; # only one contag per indiv per gen
}
}
else
{
while(abs(@{ $input ->{POPULATION} }[$b] -> { LOCATION }}[0]
- @{ $input ->{POPULATION} }[$chosen_one] ->{ LOOCATION }[0]) > 0
|| abs(@{ $input ->{POPULATION} }[$b] -> { LOCATION }[1]
- @{ $input ->{POPULATION} }[$chosen_one] -> { LOCATION }[1]) > 0)
{ # replace with random other string
my $chos_rand = rand();
$chosen_one = floor($chos_rand*$popsize);
}
@{ $input ->{POPULATION} }[$b] ->{TRAIT} = @{ $input ->{POPULATION} }[$chosen_one] ->{TRAIT};
my $xcoord = @{ $input ->{POPULATION} }[$b] -> { LOCATION }}[0]; # direct access, better ??
my $ycoord = @{ $input ->{POPULATION} }[$b] -> { LOCATION }}[1]; # yes, same method for string access
my $trait = @{ $input ->{POPULATION} }[$b] -> { TRAIT };

$contag_events++;
next;
}
}
}
return $input;
}
#--------------------------------------------------------------------
sub migrate() # rather similar to reproduce
{
my $input = $_[0];
my $migrats = 0; # how many
for(my $b=0;$b<=$popsize-1;$b++)
{
my $rand = rand();
if($rand < $mig_rate)
{ # choose
$rand = rand(); # random direction
my $xcoord = @{ $input ->{POPULATION} }[$b] ->{LOCATION}[0]];
my $ycoord = @{ $input ->{POPULATION} }[$b] ->{LOCATION}[1]];
if($rand <= 0.125 && $xcoord >0 && $ycoord >0) # go up and left
{
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[0]]--;
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[1]]--;
$pop[$xcoord][$ycoord]--;
$pop[$xcoord-1][$ycoord-1]++;
$migrats++;
}
elsif($rand <= 0.25 && $xcoord >0) # go straight up
{
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[0]]--;
$pop[$xcoord-1][$ycoord]++;
$pop[$xcoord][$ycoord]--;
$migrats++;
}
elsif($rand <= 0.375 && $xcoord >0 && $ycoord <$cols-1) # go up and right
{
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[0]]--;
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[1]]++;
$pop[$xcoord-1][$ycoord+1]++;
$pop[$xcoord][$ycoord]--;
$migrats++;
}
elsif($rand <= 0.5 && $ycoord <$cols-1) # go straight right
{
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[1]]++;
$pop[$xcoord][$ycoord+1]++;
$pop[$xcoord][$ycoord]--;
$migrats++;
}
elsif($rand <= 0.625 && $xcoord <$line-1 && $ycoord <$cols-1) # go down and right
{

@{ $input ->{POPULATION} }[$b] ->{LOCATION}[0]]++;
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[1]]++;
$pop[$xcoord+1][$ycoord+1]++;
$pop[$xcoord][$ycoord]--;
$migrats++;
}
elsif($rand <= 0.75 && $xcoord <$line-1) # go straight down
{
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[0]]++;
$pop[$xcoord+1][$ycoord]++;
$pop[$xcoord][$ycoord]--;
$migrats++;
}
elsif($rand <= 0.825 && $xcoord < $line-1 && $ycoord > 0) # go down and left
{
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[0]]++;
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[1]]--;
$pop[$xcoord+1][$ycoord-1]++;
$pop[$xcoord][$ycoord]--;
$migrats++;
}
elsif($ycoord >0) # go straight left
{
@{ $input ->{POPULATION} }[$b] ->{LOCATION}[1]]--;
$pop[$xcoord][$ycoord-1]++;
$pop[$xcoord][$ycoord]--;
$migrats++;
}
}
}
return $input;
}
#--------------------------------------------------------------------------------------------#
sub evenly_initialise() # initialise population
{
my @seq_array; # initialise array for seqs
my $indiv_fitness = 0; # fitness of string, only used when seln. operating
my $av_fitness = 0; # for whole pop, only used when seln. operating
my $st_dev = 0; # ditto
for(my $x=0; $x<=$line-1; $x++)
{
for(my $y=0; $y<=$cols-1; $y++)
{
if($popsize < ($line*$cols)) { die "popsize too small" };
for(my $z=0;$z<=($popsize/($line*$cols))-1;$z++) # run through pop
{
my @one_seq; # re-initialise each string
my $rand = rand(); # decide on horiz trait state
my $horiz_trait;
my $initial_id;
if ($rand < 0.25)
{
$horiz_trait = "A";
}
elsif ($rand < 0.5)
{
$horiz_trait = "B";
}
elsif ($rand < 0.75)
{
$horiz_trait = "C";
}
else
{
$horiz_trait = "O";
}
$rand = rand(); # decide on vertical trait state
if ($rand < 0.25)
{
$initial_id = 1;
}
elsif ($rand < 0.5)
{
$initial_id = 2;
}
elsif ($rand < 0.75)
{
$initial_id = 3;
}
else
{
$initial_id = 4;
}
my $new_seq =
{
LOCATION => [ $x, $y ], # all are initially in square 0,0
SERIAL_NUM => $initial_id, # for lineage mapping
TRAIT => $horiz_trait, # will pass by contagion
};
push @seq_array, $new_seq;
}
}
}
# RECORD OF POP
my $new_pop =
{
POPULATION => [ @seq_array ],
};
return $new_pop;
}
#--------------------------------------------------------------------------------------------#
sub disp_calc() # calculates dispersals, (optional - commented out above, try adding some output code of your own)
{
my($gene_state, $trait_state) = @_;
my $total_genes = my $total_traits = my $nbrd_genes = my $nbrd_traits =0;
my @genes = @$gene_state;
my @traits = @$trait_state;
for(my $x=0; $x<=$line-1; $x++)
{
for(my $y=0; $y<=$cols-1; $y++)
{
if($genes[$x][$y] >= 0.5)
{
$total_genes++;
unless($x == 0 || $y == 0 || $x == $line-1 || $y == $cols-1)
{
if($genes[$x+1][$y] >= 0.5
|| $genes[$x-1][$y] >= 0.5
|| $genes[$x][$y+1] >= 0.5
|| $genes[$x][$y-1] >= 0.5
|| $genes[$x+1][$y+1] >= 0.5
||$genes[$x-1][$y-1] >= 0.5
|| $genes[$x+1][$y-1] >= 0.5
|| $genes[$x-1][$y+1] >= 0.5)
{
$nbrd_genes++;
}
}
else
{
if($x == 0 && $y == 0) # top left
{
if($genes[$x+1][$y] >= 0.5
|| $genes[$x][$y+1] >= 0.5
|| $genes[$x+1][$y+1] >= 0.5)
{
$nbrd_genes++;
}
}
elsif($x == 0 && $y == $cols-1) # top right
{
if($genes[$x+1][$y] >= 0.5
|| $genes[$x][$y-1] >= 0.5
|| $genes[$x+1][$y-1] >= 0.5)
{
$nbrd_genes++;
}
}
elsif($x == $line-1 && $y == 0) # bottom left
{
if($genes[$x-1][$y] >= 0.5
|| $genes[$x][$y+1] >= 0.5
|| $genes[$x-1][$y+1] >= 0.5)
{
$nbrd_genes++;
}
}
elsif($x == $line-1 && $y == $cols-1) # bottom right
{
if($genes[$x-1][$y] >= 0.5
|| $genes[$x][$y-1] >= 0.5
|| $genes[$x-1][$y-1] >= 0.5)
{
$nbrd_genes++;
}
}
elsif($x == 0) # top row
{
if($genes[$x+1][$y] >= 0.5
|| $genes[$x][$y+1] >= 0.5
|| $genes[$x][$y-1] >= 0.5
|| $genes[$x+1][$y+1] >= 0.5
|| $genes[$x+1][$y-1] >= 0.5)
{
$nbrd_genes++;
}
}
elsif($y == 0) # left column
{
if($genes[$x+1][$y] >= 0.5
|| $genes[$x-1][$y] >= 0.5
|| $genes[$x][$y+1] >= 0.5
|| $genes[$x+1][$y+1] >= 0.5
|| $genes[$x-1][$y+1] >= 0.5)
{
$nbrd_genes++;
}
}
elsif($x == $line-1) # bottom row
{
if($genes[$x-1][$y] >= 0.5
|| $genes[$x][$y+1] >= 0.5
|| $genes[$x][$y-1] >= 0.5
||$genes[$x-1][$y-1] >= 0.5
|| $genes[$x-1][$y+1] >= 0.5)
{
$nbrd_genes++;
}
}
elsif($y == $cols-1) # right column
{
if($genes[$x+1][$y] >= 0.5
|| $genes[$x-1][$y] >= 0.5
|| $genes[$x][$y-1] >= 0.5
||$genes[$x-1][$y-1] >= 0.5
|| $genes[$x+1][$y-1] >= 0.5)
{
$nbrd_genes++;
}
}
}
}
if($traits[$x][$y] >= 0.5)
{
$total_traits++;
unless($x == 0 || $y == 0 || $x == $line-1 || $y == $cols-1)
{
if($traits[$x+1][$y] >= 0.5
|| $traits[$x-1][$y] >= 0.5
|| $traits[$x][$y+1] >= 0.5
|| $traits[$x][$y-1] >= 0.5
|| $traits[$x+1][$y+1] >= 0.5
||$traits[$x-1][$y-1] >= 0.5
|| $traits[$x+1][$y-1] >= 0.5
|| $traits[$x-1][$y+1] >= 0.5)
{
$nbrd_traits++;
}
}
else
{
if($x == 0 && $y == 0) # top left
{
if($traits[$x+1][$y] >= 0.5
|| $traits[$x][$y+1] >= 0.5
|| $traits[$x+1][$y+1] >= 0.5)
{
$nbrd_traits++;
}
}
elsif($x == 0 && $y == $cols-1) # top right
{
if($traits[$x+1][$y] >= 0.5
|| $traits[$x][$y-1] >= 0.5
|| $traits[$x+1][$y-1] >= 0.5)
{
$nbrd_traits++;
}
}
elsif($x == $line-1 && $y == 0) # bottom left
{
if($traits[$x-1][$y] >= 0.5
|| $traits[$x][$y+1] >= 0.5
|| $traits[$x-1][$y+1] >= 0.5)
{
$nbrd_traits++;
}
}
elsif($x == $line-1 && $y == $cols-1) # bottom right
{
if($traits[$x-1][$y] >= 0.5
|| $traits[$x][$y-1] >= 0.5
|| $traits[$x-1][$y-1] >= 0.5)
{
$nbrd_traits++;
}
}
elsif($x == 0) # top row
{
if($traits[$x+1][$y] >= 0.5
|| $traits[$x][$y+1] >= 0.5
|| $traits[$x][$y-1] >= 0.5
|| $traits[$x+1][$y+1] >= 0.5
|| $traits[$x+1][$y-1] >= 0.5)
{
$nbrd_traits++;
}
}
elsif($y == 0) # left column
{
if($traits[$x+1][$y] >= 0.5
|| $traits[$x-1][$y] >= 0.5
|| $traits[$x][$y+1] >= 0.5
|| $traits[$x+1][$y+1] >= 0.5
|| $traits[$x-1][$y+1] >= 0.5)
{
$nbrd_traits++;
}
}
elsif($x == $line-1) # bottom row
{
if($traits[$x-1][$y] >= 0.5
|| $traits[$x][$y+1] >= 0.5
|| $traits[$x][$y-1] >= 0.5
||$traits[$x-1][$y-1] >= 0.5
|| $traits[$x-1][$y+1] >= 0.5)
{
$nbrd_traits++;
}
}
elsif($y == $cols-1) # right column
{
if($traits[$x+1][$y] >= 0.5
|| $traits[$x-1][$y] >= 0.5
|| $traits[$x][$y-1] >= 0.5

||$traits[$x-1][$y-1] >= 0.5
|| $traits[$x+1][$y-1] >= 0.5)
{
$nbrd_traits++;
}
}
}
}
}
}
my $g_dispersal;
($total_genes > 0) ? ($g_dispersal = 1-($nbrd_genes/$total_genes)) : ($g_dispersal = 1);
my $t_dispersal;
($total_traits > 0) ? ($t_dispersal = 1-($nbrd_traits/$total_traits)) : ($t_dispersal = 1); # try writing some output code here
}