fourier01_02.r

#checker board pattern used to centre the Fourier spectrum:
checkerboard <- (-1)^(row(mat_clown) + col(mat_clown))

#modify matrix with checkerboard pattern:
mat_checker <- mat_clown*checkerboard

#Discrete fast Fourier transform:
mat_fft <- fft(mat_checker)

#magnitude in frequency domain
#Modulus =  length of the vector of the complex number:
magni <- Mod(mat_fft)

#phase in the frequency domain
#Argument = angle of the vector of the complex number:
phase <- Arg(mat_fft)

#Show magnitude in frequency domain (= spectrum):
par(mar = c(0,0,0,0), oma = c(0,0,0,0))
image(1:nrow(magni), 1:ncol(magni), log(magni + 1), col = grey((0:255)/255))