fastmatrix (version 0.5-7721)

lu-methods: Reconstruct the L, U, or X matrices from an LU object

Description

Returns the original matrix from which the object was constructed or the components of the factorization.

Usage

constructX(x)
extractL(x)
extractU(x)

Value

constructX returns \(\bold{X}\), the original matrix from which the lu

object was constructed (because of the pivoting the \(\bold{X}\) matrix is not exactly the product between \(\bold{L}\) and \(\bold{U}\)).

extractL returns \(\bold{L}\). This may be pivoted.

extractU returns \(\bold{U}\).

Arguments

x

object representing an LU factorization. This will typically have come from a previous call to lu.

See Also

lu.

Examples

a <- matrix(c(10,-3,5,-7,2,-1,0,6,5), ncol = 3)
z <- lu(a)
L <- extractL(z)
L
U <- extractU(z)
U
X <- constructX(z)
all(a == X)