RCOND Reciprocal Condition Number Estimate

Section: Array Generation and Manipulations

Usage

The rcond function is a FreeMat wrapper around LAPACKs function XGECON, which estimates the 1-norm condition number (reciprocal). For the details of the algorithm see the LAPACK documentation. The syntax for its use is 
   x = rcond(A)

where A is a matrix.

Example

Here is the reciprocal condition number for a random square matrix 
--> A = rand(30);
--> rcond(A)

ans = 
 3.5040e-04

And here we calculate the same value using the definition of (reciprocal) condition number 

--> 1/(norm(A,1)*norm(inv(A),1))

ans = 
 3.5040e-04

Note that the values are very similar. LAPACKs rcond function is far more efficient than the explicit calculation (which is also used by the cond function.