Creating and Manipulating Models | ![]() ![]() |
The remaining LTI properties are specific to one of the four model types (TF, ZPK, SS, or FRD). For single LTI models, these are summarized in the following four tables. The property values differ for LTI arrays. See set
for more information on these values.
Most of these properties are dedicated to storing the model data. Note that the matrix is set to
[]
(the empty matrix) for standard state-space models, a storage-efficient shorthand for the true value .
The Variable
property is only an attribute of TF and ZPK objects. This property defines the frequency variable of transfer functions. The default values are 's'
(Laplace variable ) in continuous time and
'z'
(Z-transform variable ) in discrete time. Alternative choices include
'p'
(equivalent to ) and
'q'
or 'z^-1'
for the reciprocal of the
variable. The influence of the variable choice is mostly limited to the display of TF or ZPK models. One exception is the specification of discrete-time transfer functions with
tf
(see tf
for details).
Note that tf
produces the same result as filt
when the Variable
property is set to 'z^-1'
or 'q'
.
Finally, the StateName
property is analogous to the InputName
and OutputName
properties and keeps track of the state names in state-space models.
![]() | Generic Properties | Setting LTI Properties | ![]() |