15.5.528 sc

sc, x, s, c

Returns a sine-cosine transform of the first dimension of numerical data x. x may be of any positive size. In s and c are returned the sine and cosine coefficients; element i corresponds to wavelength num_elem(x)/i. Sine transform: s(i) = 2 * mean(x * sin(#2pi * i * indgen(x)/num_elem(x))), but without prefactor 2 for i = 0. Cosine transform: c(i) = 2 * mean(x * cos(#2pi * i * indgen(x)/num_elem(x))), but without prefactor 2 for i = 0. For quickest calculation, the length of the first dimension of x should only contain small prime factors, like 2, 3, and 5.

The values s(0,...) are always equal to zero. If the number of elements in the first dimension is even, then s(*-1,...) is also equal to zero.

Reverse: scb

See also: power, fft, hilbert