# delmvar

Remove one matrix variable from LMI problem

## Syntax

```newsys = delmvar(lmisys,X)
```

## Description

`delmvar` removes the matrix variable X with identifier `X` from the list of variables defined in `lmisys`. The identifier `X` should be the second argument returned by `lmivar` when declaring X. All terms involving X are automatically removed from the list of LMI terms. The description of the resulting system of LMIs is returned in `newsys`.

## Examples

Consider the LMI

`$0<\left(\begin{array}{cc}{A}^{T}Y+{B}^{T}YA+Q& CX+D\\ {X}^{T}{C}^{T}+{D}^{T}& -\left(X+{X}^{T}\right)\end{array}\right)$`

involving two variables X and Y with identifiers `X` and `Y`. To delete the variable X, type

```lmisys = delmvar(lmisys,X) ```

Now `lmisys` describes the LMI

`$0<\left(\begin{array}{cc}{A}^{T}YB+{B}^{T}YA+Q& D\\ {D}^{T}& 0\end{array}\right)$`

with only one variable Y. Note that Y is still identified by the label `Y`.

## Version History

Introduced before R2006a