R: Reconstruct the L, U, or X Matrices from an LU object

lu-methods {fastmatrix} | R Documentation

## 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

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

### 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}.

### 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)

[Package fastmatrix version 0.3-819 Index]