User`s guide

Manipulating C o mplex-Valued Data
Manipulating Complex-Valued Data
In this section...
“Supported Operations for Complex D ata” on page 1-131
“Processing Complex iddata Signals at the Com m and Line” on page 1-131
Supported Operations for Complex Data
System Identification Toolbox estimation algorithms support complex data.
For example, the following estimation commands estimate complex models
from complex data:
ar, armax, arx, bj, covf, ivar, iv4, oe , pem, spa,and
n4sid.
Model transformation routines, such as
freqresp and zp kdat a,workfor
complex-valued models. However, they do no t prov ide pole-zero confidence
regions. For complex models, the parameter variance-covariance information
refers to the complex-valued parameters and the accuracy of the real and
imaginary is not com puted separately.
The display commands
compare and plot also work with complex-valued
data and models, but only show the absolute values of the signals. To plot
the real and imaginary parts of the data separately, use
plot(real(data))
and plot( imag (data)), respectively.
Processing Complex iddata Signals at the Command
Line
If the idd ata object data contains complex values, you can use the following
commands to process the complex data and create a n e w
iddata object.
Command
Descripti
on
abs(data)
Absolute value o f complex signals in iddata object.
angle(data)
Phase angle (in radians) of each complex signals in
iddata object.
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