|MATLAB Function Reference|
Matrix reciprocal condition number estimate
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
rcond is a more efficient, but less reliable, method of estimating the condition of a matrix.
rcond uses LAPACK routines to compute the estimate of the reciprocal condition number:
 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.