use PDL;
use PDL::Graphics::PGPLOT;
#my $win1 = dev('/GW', {Aspect => 1, WindowWidth => 7});
$x = xlinvals(zeroes(100,100), -5, 5); 
$y = ylinvals(zeroes(100,100), -5, 5); 
$z = sin($x*$y/2); 
imag $z; hold; 
#Show the partial derivatives wrt. x & y as vectors 
$xcomp = $x*cos($x*$y/2)/2; 
$ycomp = $y*cos($x*$y/2)/2; 
  #We want to show only every sixth vector for clarity 
$s = '0:-1:10,0:-1:10'; 
  #Finally we need to map the final 10x10 array to the 100x100 image 
$tr = pdl(0,10,0,0,0,10); 
vect $xcomp->slice($s), $ycomp->slice($s), {Transform=>$tr};