DCL:MATH2:FFTLIB: Fast Fourier Transformation: Explanation of Subroutines
Performs sine transformation only on odd wavenumber components: SINQI initializes; SINQF performs forward sine transformation; and SINQB performs inverse sine transformation.
Forward transformation is defined as follows:
Inverse transformation is defined as follows:
CALL SINQI(N,WSAVE)
CALL SINQF(N,R,WSAVE)
CALL SINQB(N,R,WSAVE)
N (I) Length of data to process. WSAVE (R) Working array. Must have length of at least 3 N+15. R (R) Floating-point array to process. It is both the input and output parameter. (See above definition.)