# Definition of function representing a chequer board pattern chequer(x,y) = (floor(x)+floor(y))%2 * tophat(hypot(x,y),3) # Take FFT of disk fft [-40:40:0.1][-40:40:0.1] fft() of chequer() w = unit(5*cm) set numerics complex set nogrid set key below set nocolorkey set sample grid 300x300 set size w square set multiplot set nodisplay # Plot real-space image plot [-4:4][-4:4] chequer(x,y) with colormap # Plot Fourier-domain image set origin w+unit(5*mm),0 set axis y right plot [-2.5:2.5][-2.5:2.5] abs(fft(x,y)) with colormap set display refresh