Cfft1b Cfft1f Cfft1i Cfftmb Cfftmf Cfftmi

Cfft1i() Sub Cfft1i ( N As  Long, Wsave() As  Double, Info As  Long  ) Initialization of work data for Cfft1f and Cfft1b Purpose This routine initializes array Wsave() for use in its companion routines Cfft1f and Cfft1b. The prime factorization of N together with a tabulation of the trigonometric functions are computed and stored in array Wsave(). Note - The initialization of Wsave() is not necessary for the succeeding call of Cfft1f or Cfft1b for the same N value. If the value of N has been changed, Wsave() should be re-initialized by this routine. Parameters [in] N The length of the sequence to be transformed. (N >= 1) (The transform is most efficient when N is a product of small primes) [out] Wsave() Array Wsave(LWsave - 1) (LWsave >= 2*N + ln(N)/ln(2) + 4) Work data, containing the prime factors of N and also containing certain trigonometric values which will be used in routines Cfft1f and Cfft1b. [out] Info = 0: Successful exit. = -1: The argument N had an illegal value. (N < 1) = -2: The argument Wsave() is invalid. Reference FFTPACK Example Program See example of Cfft1f.