inv

Scilab Function
Last update : 25/04/2007

inv - matrix inverse

### Calling Sequence

  `inv(X)`

### Parameters

- `X` : real or complex square matrix, polynomial matrix, rational matrix in transfer or state-space representation.

### Description

`inv(X)` is the inverse of the square matrix `X` . A warning message is printed if `X` is badly scaled or nearly singular.

For polynomial matrices or rational matrices in transfer representation, `inv(X)` is equivalent to `invr(X)` .

For linear systems in state-space representation (`syslin` list), `invr(X)` is equivalent to `invsyslin(X)` .

### References

`inv` function for matrices of numbers is based on the Lapack routines DGETRF, DGETRI for real matrices and ZGETRF, ZGETRI for the complex case. For polynomial matrix and rational function matrix `inv` is based on the `invr` Scilab function.

### Examples

    A=rand(3,3);inv(A)*A
    //
    x=poly(0,'x');
    A=[x,1,x;x^2,2,1+x;1,2,3];inv(A)*A
    //
    A=[1/x,2;2+x,2/(1+x)]
    inv(A)*A
    //
    A=ssrand(2,2,3);
    W=inv(A)*A
    clean(ss2tf(W))

### See Also

`slash` , `backslash` , `pinv` , `qr` , `lufact` , `lusolve` , `invr` , `coff` , `coffg` ,