Computes discrete fast Fourier transform of river discharge data and the derived metrics.
The methods are described in J. L. Sabo, D. M. Post (2008) and J. L. Sabo, A. Ruhi, G. W. Holtgrieve, V. Elliott, M. E. Arias, P. B. Ngor, T. A. Räsänsen, S. Nam (2017) .