User`s guide

1 Data Processing
Resampling Data
In this section...
“WhatIsResampling?”onpage1-100
“Resampling D ata Using the GUI” on page 1-101
“Resampling Da ta a t the Comman d Line” on pa ge 1-101
“Resampling Data Without Aliasing Effects” on page 1-103
“See Also” on page 1-106
What Is Resampling?
Resampling data signals in the System Identification Toolbox product applies
an antialiasing (lowpass) FIR filter to the data and changes the sampling rate
of the signal by decimation or interpolation.
If your data is sample d faster than needed during the experiment, you can
decimate it without information loss. If your data is sampled more s low ly
than needed, there is a possibility that you miss important information
about the dynamics at higher frequencies. Although you can resample the
data at a higher rate, the resampled values occurring betw een measure d
samples do n ot represent me asured information about your system. Instead
of resampling, repeat the experiment using a higher sampling rate.
Tip You should decimate y our data when it contains high-frequency noise
outside the frequency range of the system dynamics.
Resampling takes into account how the data behaves between samples, which
you specify when you import the data into the System Identification Tool
GUI (zero-order or first-order hold). For more information about the data
properties you specify before importing the data, see “Representing Data in
the GUI” on page 1-13.
You can resa mple data usin g the System Identification To ol GUI or the
resample command. You can only resample time-domain data at uniform
time intervals.
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