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# 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.