nehari Nehari approximant of continuous time dynamical systems

## Syntax

                x = nehari(R)
                x = nehari(R, tol)

## Arguments

R

  a continuous time linear dynamical system in state-space representation.

x

  a continuous time linear dynamical system in state-space representation.

tol

  optional threshold, default value is 1e-6.

## Description

`[x]=nehari(R [,tol])returns` the Nehari approximant of `R`.

`R` = linear system in state-space representation (`syslin` list).

`R` is strictly proper and `- R~` is stable (i.e. `R` is anti stable).

    || R - X ||oo = min || R - Y ||oo
                  Y in Hoo

## History

5.4.0 `Sl` is now checked for continuous time linear dynamical system. This modification has been introduced by this commit