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

Chapter 5 Fast Fourier Transforms 589
Simultaneous real-to-complex one-dimensional FFT SRCFTS/DRCFTS
For an inverse complex-to-real transform, the real part
of the i-th data point of the j-th data set, 1 ≤ i ≤ l/2+1, 1
≤ j ≤ n, is stored in
and the imaginary part is stored in
respectively.
l Number of data points in each complete data set, l > 0.
incl Storage increment between successive elements of the
same data set, incl > 0. incl = 1 means that the data
points of a real data set are stored contiguously in
array x, or that the real and imaginary parts of the
data points of a complex data set are stored
alternatingly in contiguous elements of x.
n The number of data sets, n > 0.
incn Storage increment between corresponding data points
of successive data sets, incn > 0.
iopt Option flag:
iopt ≥ 0 Compute forward transform.
iopt < 0 Compute inverse transform.
Output x The transformed data replaces the input if ier = 0 is
returned. Unchanged if ier < 0.
For a forward real-to-complex transform, the real part
of the i-th output point of the j-th data set, 1 ≤ i ≤ l/2+1,
1 ≤ j ≤ n, is stored in
and the imaginary part is stored in
respectively. If needed, the remaining (l/2 − 1) × n
complex output values may be formed by using the
conjugate-symmetry condition.
For an inverse complex-to-real transform, the i-th real
output point of the j-th data set, 1 ≤ i ≤ l, 1 ≤ j ≤ n, is
stored in
x 2 i× 2–()incl× j 1–()+ incn× 1+()
x 2 i× 1–()incl× j 1–()+ incn× 1+()
x 2 i× 2–()incl× j 1–()+ incn× 1+()
x 2 i× 1–()incl× j 1–()+ incn× 1+(),
x i 1–()incl× j 1–()+ incn× 1+().