WCfft1b WCfft1b2 WCfft1f WCfft1f2 WCost1b WCost1f WRfft1b WRfft1f WSint1b WSint1f

WCost1f() Function WCost1f ( N As  Long, R As  Variant  ) One-dimensional cosine transform Purpose WCost1f computes the one-dimensional Fourier transform of an even sequence within a real array. This is referred to as the forward transform or Fourier analysis, transforming the sequence from physical to spectral space. R(0) = (1/2)R(0)/(N-1) + ΣR(j)/(N-1) + (1/2)R(N-1)/(N-1) (Σ for j = 1 to N-2) R(k) = R(0)/(N-1) + Σ2x[j)cos(πjk/(N-1)) + (-1)^k R(N-1)/(N-1) (Σ for j = 1 to N-2) (k = 1 to N-2) R(N-1) = (1/2)R(0)/(N-1) + ΣR(j)(-1)^k/(N-1) + (1/2)(-1)^(N-1) R(N-1)/(N-1) (Σ for j = 1 to N-2) This transform is normalized since a call to WCost1f followed by a call to WCost1b (or vice-versa) reproduces the original array subject to algorithmic constraints, roundoff error, etc. Returns N x 1 Column 1 Rows 1 to N Cosine transformed data sequence Parameters [in] N The length of the sequence to be transformed. (N >= 1) The transform is most efficient when N - 1 is a product of small primes. [in] R (N) The sequence to be transformed. Reference FFTPACK Example Compute the cosine transform of the data sequence by WCost1f. Then compute its backward transform by WCost1b and confirm that the original data sequence is restored.