% trigfield7.m allows you to explicitly choose wavenumbers

gridsize = [80 80];                           % number of grid points in x, y
gridrange= [0 15 0 15];                       % default [xmin xmax ymin ymax]
[x,y]    = easygrid(gridrange, gridsize);     % matrices of x and y values
Z        = [];

K = [[2 0]; [0 1]; [1 1]];                          % wave numbers
K = [[1 0]; [0 1]; [-1 0]; [0 -1]];
mm=100;
K = [cos(2*pi*(0:mm)/mm)' sin(2*pi*(0:mm)/mm)'];
m = length(K(:,1));                           % number of modes

A        = randn(1,m)*sqrt(2/m);              % amplitudes of Fourier modes
phi      = 2 * pi * rand(m,1);                % random phase

for i=1:gridsize(1),                          % step through grid points
  for j=1:gridsize(2),
    Z(i,j) = A * cos(K*[x(i,j); y(i,j)] + phi); % compute field value at x,y
  end
end

subplot(3,2,1)
mesh(x,y,Z)
view(-10,30)
xlabel('Horizontal');
ylabel('Vertical');
zlabel('Intensity');
title('Surface plot');

subplot(3,2,2)
pcolor(x,y,Z>0)
shading flat
title('Level sets')

subplot(3,2,3)
contour(x,y,Z,20)
title('Contour plot')

subplot(3,2,4)
pcolor(x,y,Z)
shading flat
title('Intensity plot')

subplot(3,2,5)
hist(reshape(Z,1,gridsize(1)*gridsize(2)))
title('Histogram of field values')

subplot(3,2,6)
plot(K(:,1),K(:,2),'*')
maxcoord = max(max(abs(K)));
axis([-maxcoord maxcoord -maxcoord maxcoord]);
title('Wavenumbers K')