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# rcond

inverse condition number

### Syntax

rcond(X)

### Arguments

- X
real or complex square matrix

### Description

`rcond(X)`

is an estimate for the reciprocal of the
condition of `X`

in the 1-norm.

If `X`

is well conditioned, `rcond(X)`

is close to 1.
If not, `rcond(X)`

is close to 0.

We compute the 1-norm of A with Lapack/DLANGE, compute its LU decomposition with Lapack/DGETRF and finally estimate the condition with Lapack/DGECON.

### Examples

A=diag([1:10]); rcond(A) A(1,1)=0.000001; rcond(A)

Estimating the 1-norm inverse condition number with `rcond`

is
much faster than computing the 2-norm condition number with `cond`

.
As a trade-off, `rcond`

may be less reliable.

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