XSPEC Name
XSPEC Purpose
Compute an ensemble averaged cross spectrum of real data.
Category
Calling Sequence
sxy = xspec(x,y,n,sr,[freq]) Inputs
x = input signal number 1. in
y = input signal number 2. in
If x or y have too few points, -1 is returned.
n = number of points to use in each transform in
May be arbitrary.
sr = sample rate in Hz (Def=1 Hz) in
Needed to get actual units.
Keyword Parameters
Keywords
OVERLAP=novr number of points to overlap spectra.
(Def=0).
TRANSFER_FUNCT = transfer function, Txy = Sxy/Sxx
in units of y/x
CA_ARRAY = ca : Coherence and autospectra array.
ca(*,0)=Cxy(f) Coherence=|Sxy|^2/(Sxx*Syy) dimensnless
ca(*,1) = Sxx(f) Autospectrum of x in units of x**2/Hz.
ca(*,2) = Syy(f) Autospectrum of y in units of y**2/Hz.
N_ENSEMBLE=n returned # spectra ensemble averaged.
/NOTES lists some additional comments.
Outputs
sxy = spectral density in units of x*y/Hz. out
First value is DC, last is Nyquist.
freq = optionally output frequency array. out
Common Blocks
xspec_com Notes
Notes: Restricted to one dimensional data only.
Reference
Modification History
B. L. Gotwols Mar. 1, 1993
R. E. Sterner Mar. 1, 1993 --- cleaned up some.
BLG, RES --- Mar. 10, 1993 --- renamed variables.
BLG --- 19 May, 1993 --- made loop index long.
Fixed ntimes to be correct. Also floated sr.
Made OVERLAP default to 0 to be consistent with
future addition of OVERLAP in rspec and cspec.
Copyright (C) 1993, Johns Hopkins University/Applied Physics Laboratory
This software may be used, copied, or redistributed as long as it is not
sold and this copyright notice is reproduced on each copy made. This
routine is provided as is without any express or implied warranties
whatsoever. Other limitations apply as described in the file disclaimer.txt.