rcond (MATLAB Functions)

Matrix reciprocal condition number estimate

Syntax

```
c = rcond(A)
```

Description

c = rcond(A) returns an estimate for the reciprocal of the condition of A in 1-norm using the LAPACK condition estimator. If A is well conditioned, rcond(A) is near 1.0. If A is badly conditioned, rcond(A) is near 0.0. Compared to cond, rcond is a more efficient, but less reliable, method of estimating the condition of a matrix.

Algorithm

For full matrices A, rcond uses the LAPACK routines listed in the following table to compute the estimate of the reciprocal condition number.

Real
Complex

A double
DLANGE, DGETRF, DGECON
ZLANGE, ZGETRF, ZGECON

A single
SLANGE, SGETRF, SGECON
CLANGE, CGETRF, CGECON

	Real	Complex
`A` `double`	DLANGE, DGETRF, DGECON	ZLANGE, ZGETRF, ZGECON
`A` `single`	SLANGE, SGETRF, SGECON	CLANGE, CGETRF, CGECON

See Also

cond, condest, norm, normest, rank, svd

References

[1] Anderson, E., Z. Bai, C. Bischof, S. Blackford, J. Demmel, J. Dongarra, J. Du Croz, A. Greenbaum, S. Hammarling, A. McKenney, and D. Sorensen, LAPACK User's Guide (http://www.netlib.org/lapack/lug/ lapack_lug.html), Third Edition, SIAM, Philadelphia, 1999.

rbbox real