User`s guide

Extracting and Modifying Subsystems
3-9
is equivalent to
sys(1,[2 4 5]
Similarly, if pressure isthenameassignedtoanoutputchanneloftheLTI
model
sys,then
sys('pressure',1) = tf(1, [1 1])
reassigns the subsystem from the first i nput of sys to the output labeled
pressure.
You ca n reference a set of channels by input or output name by using a cell
array of strings for the names. For example, if
sys has one output channel
named
pressure and one named temperature,thent hese two output channels
can b e referenced using
sys({'pressure','temperature'})
Resizing LTI Systems
Resizing a system consists of adding or deleting inputs and/or outputs. To
delete the first two inputs, simply type
sys(:,1:2) = []
In deletions, at least one of the row/column indexes should be the colon (:)
selector.
To perform input/output augmentation, you can proceed by concatenat ion or
subassignment. Given a system
sys with a single input, you can add a second
input using
sys = [sys,h];
or, equivale ntly, using
sys(:,2) = h;
where h is any LTI model wit h one input, and the same numb er of outputs as
sys. There is an important difference between these two options: while
concatenationobeystheprecedencerules(seepage2-5),subsystemassignment
does not alter the model type. So, if
sys and h are TF and SS o bjects,
respectively, the first statement produces a state-space model, and t he second
statement produces a transfer function.