User`s guide

LTI Properties
2-33
Direct Property Referencing
An alternative way t o q uery /mo d ify pro p ert y values is by s tructure- lik e
referencing. Recall t h at LTI ob jec ts are ba si c MAT L A B s tructure s ex cep t for
the additional f lag that marks them as TF, ZPK , S S, or F RD obj ects ( se e page
2-3). The field names for LTI objects are the property names, so you can
retrieve or modify property values with the structure-like syntax.
PropertyValue = sys.PropertyName% gets property value
sys.PropertyName = PropertyValue% sets property value
These commands are respectively equivalent to
PropertyValue = get(sys,'PropertyName')
set(sys,'PropertyName',PropertyValue)
For example, type
sys = ss(1,2,3,4,'InputName','u');
sys.a
and you get the value of the property “a” for the state- space mod el sys.
ans =
1
Similarly,
sys.a = –1;
resets the state transition matrix for sys to –1. S ee “LTI Arrays of SS Models
with Differing Numbers o f States” on page 4-23 for information on setting the
properties of LTI arrays of state-space models w ith differentnumbers of states
in each model.
Unlike standard MATLAB structures, you do not need to type the entire field
name or use upper-case characters. You only need to type the minimum
number of characters sufficient to identify the property name uniquely. Thus
either of the commands
sys.InputName
sys.inputn