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Condition number for inversion

`C = cond(A)`

`C = cond(A,p)`

`rcond`

is a more efficient, but less reliable, method of estimating the condition of a matrix compared to`cond`

.

The algorithm for `cond`

has three pieces:

If

`p = 2`

, then`cond`

uses the singular value decomposition provided by`svd`

to find the ratio of the largest and smallest singular values.If

`p = 1`

,`Inf`

, or`'fro'`

, then`cond`

calculates the condition number using the appropriate norm of the input matrix and its inverse with`norm(A,p) * norm(inv(A),p)`

.If the input matrix is sparse, then

`cond`

ignores any specified`p`

value and calls`condest`

.