Implements the Fast Sine Transform for transformation of one-dimensional real data sets. For reference, see James S. Walker,
Fast Fourier Transforms, chapter 3 (ISBN 0849371635).
There are several variants of the discrete sine transform. The present implementation corresponds to DST-I, with various normalization conventions, which are specified by the parameter {@link DstNormalization}. It should be noted that regardless to the convention, the first element of the dataset to be transformed must be zero.
DST-I is equivalent to DFT of an odd extension of the data series. More precisely, if x0, …, xN-1 is the data set to be sine transformed, the extended data set x0#, …, x2N-1# is defined as follows
- x0# = x0 = 0,
- xk# = xk if 1 ≤ k < N,
- xN# = 0,
- xk# = -x2N-k if N + 1 ≤ k < 2N.
Then, the standard DST-I y0, …, yN-1 of the real data set x0, …, xN-1 is equal to half of i (the pure imaginary number) times the N first elements of the DFT of the extended data set x0#, …, x2N-1#
yn = (i / 2) ∑k=02N-1 xk# exp[-2πi nk / (2N)] k = 0, …, N-1.
The present implementation of the discrete sine transform as a fast sine transform requires the length of the data to be a power of two. Besides, it implicitly assumes that the sampled function is odd. In particular, the first element of the data set must be 0, which is enforced in {@link #transform(UnivariateFunction,double,double,int,TransformType)}, after sampling.
@since 1.2