October 2006 fftw fast fourier transform that use fftw library Calling Sequence [y]=fftw(x) [y]=fftw(x,sign) [y]=fftw(x,sign,dim,incr) [y]=fftw(x,sign,[dim1 dim2 ...dimN],[incr1 incr2 ...incrN]) Parameters y,x matrix/vector of real/complex data. Input/output data to be transformed. sign Integer. 1 or -1. Set direct or inverse transform. dim integer. Set the dimension (the length) of the transform. incr integer. Set the stride (the span) of the transform. Description This function realizes direct/inverse Discrete Fourier Transform (DFT) with the help of the FFTW library. One can compute vector, 2D, M-D transform with this function. For more details of fftw syntax see fft scilab function. For more details about FFTW library see FFTW Web site : http://www.fftw.org Remark : fftw function automaticaly stores his last parameters in memory to re-use it in a second time. This results on a time computation improvement when consecutives calls (with same parameters) are used. Examples //simple vector direct transform a = rand(50,1)+%i*rand(50,1); y = fftw(a); y = fftw(a,-1); //inverse transform b = fftw(y,1); //2D transform a = rand(512,512)+%i*rand(512,512); y = fftw(a); //M-D transform -old calling sequence- a = rand(120,1); y = a; dim=[5 6 4];incr=[1 5 30]; for i=1:3 y = fftw(y,-1,dim(i),incr(i)); end //M-D transform -new calling sequence- //More efficient than old y = fftw(a,-1,[5 6 4],[1 5 30]); b = fftw(y,1,[5 6 4],[1 5 30]); See Also fftw_flags get_fftw_wisdom set_fftw_wisdom fftw_forget_wisdom Bibliography Matteo Frigo and Steven G. Johnson, "FFTW Manual fo version 3.1.2" June 2006. Available : http://www.fftw.org