HP MLIB User's Guide Vol. 2 7th Ed.

Chapter 5 Fast Fourier Transforms 583
Simultaneous real-to-complex one-dimensional FFT CRCFTS/ZRCFTS
Usage VECLIB:
INTEGER*4 l, incl, n, incn, iopt, ier
COMPLEX*8 z(lenz)
CALL CRCFTS(z, l, incl, n, incn, iopt, ier)
INTEGER*4 l, incl, n, incn, iopt, ier
COMPLEX*16 z(lenz)
CALL ZRCFTS(z, l, incl, n, incn, iopt, ier)
VECLIB8:
INTEGER*8 l, incl, n, incn, iopt, ier
COMPLEX*8 z(lenz)
CALL CRCFTS(z, l, incl, n, incn, iopt, ier)
INTEGER*8 l, incl, n, incn, iopt, ier
COMPLEX*16 z(lenz)
CALL ZRCFTS(z, l, incl, n, incn, iopt, ier)
Input z Array containing n data sets, each consisting of l data
points, to be transformed. Typically, z is a two- or
three-dimensional array with each set of data being a
one-dimensional array section. Refer to “Notes” for
suggested usages.
Treating z as a one-dimensional array, results in
The i-th data point of the j-th data set, 1 ≤ i ≤ l, 1 ≤ j ≤
n, is stored in
For a forward real-to-complex transform, only real
parts of z are used as input.
For an inverse complex-to-real transform, only the first
l/2+1 complex data points of each data set are used as
input.
l Number of data points in each data set, l > 0.
incl Storage increment between successive elements of the
same data set, incl > 0. Use incl = 1 if each data set is
stored contiguously in array z.
n The number of data sets, n > 0.
incn Storage increment between corresponding data points
of successive data sets, incn > 0.
lenz l 1–()= incl× n 1–()+ incn× 1.+
z i 1–()incl× j 1–()+ incn× 1+().