y

y coordinate

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Discussion

The values Ly and Ny are set during initialization from which the y coordinate is derived.

The y coordinate is periodic, which means that

dy = Ly/Ny;
y = dy*(0:Ny-1)';

Note that this means that it is NOT true that Ly=y(end)-y(1), but in fact you need an extra grid point, i.e., it IS true that Ly = dy + y(end)-y(1). This is the usual grid for Fourier Transforms.