home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Turnbull China Bikeride
/
Turnbull China Bikeride - Disc 1.iso
/
ARGONET
/
PD
/
MATHS
/
RLAB
/
RLAB125.ZIP
/
!RLaB
/
help_jr
/
rcond
< prev
next >
Wrap
Text File
|
1996-04-09
|
961b
|
44 lines
rcond:
Syntax: rcond( A )
Description:
Rcond estimates the recipricol of the condition number of the
input matrix A. rcond() uses the LAPACK routines DGECON, or
ZGECON.
Probably the most published way to compute the condition
number of a matrix is:
Kcond = ||A|| * ||inv(A)||
Another method is to use the 1st and last singular values of
A:
Kcond = sigma(1)/sigma(n)
rcond() computes an ESTIMATE of the recipricol of the
condition number without computing all of the columns of
inv(A). For more information see the LAPACK User's Guide.
Example:
> A = [1,2,3;4,5,6;7,8,9]
A =
1 2 3
4 5 6
7 8 9
> # Get the condition number of A
> 1/rcond (A)
4.54e+17
> A[3;3] = 0
A =
1 2 3
4 5 6
7 8 0
> 1/rcond (A)
51.7
See Also inv, det, lu