diagU2N {Matrix}R Documentation

Transform Triangular Matrices from Unit Triangular to General and back

Description

Transform a triangular matrix x, i.e., of class "triangularMatrix", from (internally!) unit triangular (“unitriangular”) to “general” (diagU2N(x)) or back (diagN2U(x)).

Usage

 diagN2U(x, cl = getClassDef(class(x)))
 diagU2N(x, cl = getClassDef(class(x)), checkDense = FALSE)
.diagU2N(x, cl, checkDense = FALSE)

Arguments

x

a triangularMatrix, often sparse.

cl

(optional, for speedup only:) class (definition) of x.

checkDense

logical indicating if dense (see denseMatrix) matrices should be considered at all.

Details

The concept of unit triangular matrices with a diag slot of "U" stems from LAPACK.

Value

a triangular matrix of the same class and (semantically) with identical entries as x, but with a different diag slot.

Note

Such internal storage details should rarely be of relevance to the user. Hence, these functions really are rather internal utilities.

See Also

"triangularMatrix", "dtCMatrix".

Examples

(T <- Diagonal(7) + triu(Matrix(rpois(49, 1/4), 7,7), k = 1))
(uT <- diagN2U(T)) # "unitriangular"
stopifnot(all(T == uT),
          identical(T, diagU2N(uT)))
[Package Matrix version 1.0-6 Index]