User`s guide

1 Data Processing
When the Spect ralD ata property of individual idfrd objectsisnotempty,
horizontal and vertical concatenation handle
SpectralData,asfollows.
In case of horizontal concatenation, thereisnomeaningfulwaytocombinethe
SpectralData of individual idfrd objects and the resulting SpectralData
property is empty. An empty property results because each idfrd object has
its own set of noise channels, where the number of noise channels equals the
number of outputs. When the resulting
idfrd object contains the same output
channels as each of the individual
idfrd objects, it cannot accommodate the
noise data from all the
idfrd objects.
In case of vertical co nca ten ation, the toolbox concatenate s individual noise
models diagonally. The following shows that
data.SpectrumData is a block
diagonal matrix of the power spectra and cross spectra of the output noise in
the system:
data s
data s
dataN s
.
.
.
=
1
0
0
s in data.s is the abbreviation for the Spec trumData property name.
See Also
The following operations also create idfrd objects:
Transforming
iddata objects. For more information, see “Transforming
Between Frequency-Domain and Frequency-Response Data” on page 1-128.
Estimating nonparametric models using
etfe, spa,andspafdr.Formore
information, see “Identifying Frequency-Res po ns e Models” on pag e 3-2.
Converting the Control System Toolbox
frd object. F or more information,
see “Using Models with Control System Toolbox Softw are” on page 10-2.
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