diagU2N  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)
and .diagN2U(x)
assume without
checking that x
is a triangularMatrix
with
suitable diag
slot ("U"
and "N"
, respectively),
hence they should be used with care.
diagU2N(x, cl = getClassDef(class(x)), checkDense = FALSE)
diagN2U(x, cl = getClassDef(class(x)), checkDense = FALSE)
.diagU2N(x, cl = getClassDef(class(x)), checkDense = FALSE)
.diagN2U(x, cl = getClassDef(class(x)), 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 # still "dtC"
T < diagN2U(as(T,"triangularMatrix"))
dT < as(T, "denseMatrix") # (unitriangular)
dT.n < diagU2N(dT, checkDense = TRUE)
sT.n < diagU2N(dT)
stopifnot(is(dT.n, "denseMatrix"), is(sT.n, "sparseMatrix"),
dT@diag == "U", dT.n@diag == "N", sT.n@diag == "N",
all(dT == dT.n), all(dT == sT.n))
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