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)

Arguments

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

Value

constructX returns \(\mathbf{X}\) , the original matrix from which the lu object was constructed (because of the pivoting the \(\mathbf{X}\) matrix is not exactly the product between \(\mathbf{L}\) and \(\mathbf{U}\) ).

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

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

Seealso

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)