FFTPACK

FFTPACK is a software library used to quickly calculate the Fast Fourier Transform (FFT). The FFT is used to quickly break down complex data into simpler, easier-to-understand pieces. Think of it like turning a big mess of Legos into separate piles - it makes it easier to figure out what pieces are there and how they fit together. FFTPACK helps do this same thing with data, but much faster and more accurately.