diagU2N {Matrix}  R Documentation 
Transform a triangular matrix x
, i.e., of class
"triangularMatrix"
,
from (internally!) unit triangular (“unitriangular”) to
“general” triangular (diagU2N(x)
) or back (diagN2U(x)
).
Note that the latter, diagN2U(x)
, also sets the diagonal to one
in cases where diag(x)
was not all one.
.diagU2N(x)
assumes but does not check that x
is
a triangularMatrix
with diag
slot
"U"
, and should hence be used with care.
diagN2U(x, cl = getClassDef(class(x)), checkDense = FALSE) diagU2N(x, cl = getClassDef(class(x)), checkDense = FALSE) .diagU2N(x, cl, checkDense = FALSE)
x 
a 
cl 
(optional, for speedup only:) class (definition) of 
checkDense 
logical indicating if dense (see

The concept of unit triangular matrices with a diag
slot of
"U"
stems from LAPACK.
a triangular matrix of the same class
but with a
different diag
slot. For diagU2N
(semantically) with
identical entries as x
, whereas in diagN2U(x)
, the
offdiagonal entries are unchanged and the diagonal is set to all
1
even if it was not previously.
Such internal storage details should rarely be of relevance to the user. Hence, these functions really are rather internal utilities.
"triangularMatrix"
,
"dtCMatrix"
.
(T < Diagonal(7) + triu(Matrix(rpois(49, 1/4), 7,7), k = 1)) (uT < diagN2U(T)) # "unitriangular" (t.u < diagN2U(10*T))# changes the diagonal! stopifnot(all(T == uT), diag(t.u) == 1, identical(T, diagU2N(uT))) T[upper.tri(T)] < 5 T < diagN2U(as(T,"triangularMatrix")) stopifnot(T@diag == "U") dT < as(T, "denseMatrix") dt. < diagN2U(dT) dtU < diagN2U(dT, checkDense=TRUE) stopifnot(is(dtU, "denseMatrix"), is(dt., "sparseMatrix"), all(dT == dt.), all(dT == dtU), dt.@diag == "U", dtU@diag == "U")