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# psinfo

Inquire about polytopic or parameter-dependent systems created with psys

## Syntax

```psinfo(ps)
[type,k,ns,ni,no] = psinfo(ps)
pv = psinfo(ps,'par')
sk = psinfo(ps,'sys',k)
sys = psinfo(ps,'eval',p)
```

## Description

psinfo is a multi-usage function for queries about a polytopic or parameter-dependent system ps created with psys. It performs the following operations depending on the calling sequence:

• psinfo(ps) displays the type of system (affine or polytopic); the number k of SYSTEM matrices involved in its definition; and the numbers of ns, ni, no of states, inputs, and outputs of the system. This information can be optionally stored in MATLAB® variables by providing output arguments.

• pv = psinfo(ps,'par') returns the parameter vector description (for parameter-dependent systems only).

• sk = psinfo(ps,'sys',k) returns the k-th SYSTEM matrix involved in the definition of ps. The ranking k is relative to the list of systems syslist used in psys.

• sys = psinfo(ps,'eval',p) instantiates the system for a given vector p of parameter values or polytopic coordinates.

For affine parameter-dependent systems defined by the SYSTEM matrices S0, S1, . . ., Sn, the entries of p should be real parameter values p1, . . ., pn and the result is the LTI system of SYSTEM matrix

S(p) = S0 + p1S1 + . . .+ pnSn

For polytopic systems with SYSTEM matrix ranging in

Co{S1, . . ., Sn},

the entries of p should be polytopic coordinates p1, . . ., pn satisfying pj ≥ 0 and the result is the interpolated LTI system of SYSTEM matrix

$S=\frac{{p}_{1}{S}_{1}+\cdots +{p}_{n}{S}_{n}}{{p}_{1}+\cdots +{p}_{n}}$