Take both of the diagonals through an element in a matrixMar 2014 ⋅ c-e-731 ⋅ se/mathematica ⋅ #list-manipulation
Plotting the frequency spectrum of a data series using FourierJan 2013 ⋅ c-e-731 ⋅ se/mathematica ⋅ #fourier-analysis