rfft1b rfft1f rfft1i

rfft1i() def rfft1i ( n  , wsave    ) Initialization of work data for rfft1f and rfft1b Purpose rfft1i initializes array wsave for use in its companion routines rfft1f and rfft1b. 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 rfft1f or rfft1b for the same n value. If the value of n has been changed, wsave should be re-initialized by this routine. Returns info (int) = 0: Successful exit = -1: The argument n had an illegal value (n < 1) = -2: The argument wsave is invalid 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 Numpy ndarray (1-dimensional, float, length 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 rfft1f and rfft1b. Reference FFTPACK 5.1 Example Program See example of rfft1f.