code by will grissom that implements the clever nufft method from the following paper @a greengard:04:atn siam-rev 46 3 443-54 . 2004 Leslie Greengard June-Yub Lee Accelerating the nonuniform fast Fourier transform @u doi 10.1137/S003614450343200X if you want to run this on a PC, you will need to use the matlab "mex" command to compile the back_grid.c and forw_grid.c routines into mex executables for the PC. i don't know the specifics of how to do this on a PC but "help mex" should explain.