dst(X[, type=1])
Replaces the columns of a dense real matrix with their discrete sine transforms. The second argument, an integer between 1 and 4, denotes the type of transform (DST-I, DST-II, DST-III, DST-IV). These transforms are defined as follows (for a matrix with n rows).
idst(X[, type=1])
Replaces the columns of a dense real matrix with the inverses of the discrete sine transforms defined above.