Install cl-fftw3 by entering the following commands in the terminal:
sudo apt update sudo apt install cl-fftw3
Common Lisp package for using the FFTW3 library
This package provides an interface for Common Lisp programs to use the FFTW3 Fourier transform library. A number of higher-level interfaces has been added in addition to the native interface to the FFTW3 C-based library.