dear list,
I'm interested in using the 'dspMatrix' class of matrices, from the
R-project recommended package Matrix, to store large symmetric matrices.
I would like to know how to fill such a matrix cell by cell avoiding
coercion to a non-dspMatrix which might not be storing the symmetric
matrix so efficiently.
for instance, when i try to fill one cell in the two corresponding
triangles of a symmetric matrix:
library(Matrix)
m <- new("dspMatrix", Dim=as.integer(c(3,3)), x=rep(0, 6))
m
3 x 3 Matrix of class "dspMatrix"
[,1] [,2] [,3]
[1,] 0 0 0
[2,] 0 0 0
[3,] 0 0 0
str(m)
Formal class 'dspMatrix' [package "Matrix"] with 5 slots
..@ x : num [1:6] 0 0 0 0 0 0
..@ Dim : int [1:2] 3 3
..@ Dimnames:List of 2
.. ..$ : NULL
.. ..$ : NULL
..@ uplo : chr "U"
..@ factors : list()
m[1,2] <- m[2,1] <- 1
m
3 x 3 Matrix of class "dgeMatrix"
[,1] [,2] [,3]
[1,] 0 1 0
[2,] 1 0 0
[3,] 0 0 0
str(m)
Formal class 'dgeMatrix' [package "Matrix"] with 4 slots
..@ x : num [1:9] 0 1 0 1 0 0 0 0 0
..@ Dim : int [1:2] 3 3
..@ Dimnames:List of 2
.. ..$ : NULL
.. ..$ : NULL
..@ factors : list()
however, when i do a subset assignment of a submatrix, then it works as
expected, i.e., i get a dspMatrix as a result:
m <- new("dspMatrix", Dim=as.integer(c(3,3)), x=rep(0, 6))
m[1:2,1:2] <- 1
m
3 x 3 Matrix of class "dspMatrix"
[,1] [,2] [,3]
[1,] 1 1 0
[2,] 1 1 0
[3,] 0 0 0
str(m)
Formal class 'dspMatrix' [package "Matrix"] with 5 slots
..@ x : num [1:6] 1 1 1 0 0 0
..@ Dim : int [1:2] 3 3
..@ Dimnames:List of 2
.. ..$ : NULL
.. ..$ : NULL
..@ uplo : chr "U"
..@ factors : list()
i guess there must be some way of doing a "symmetric" assignment of a
value but I have not been able to figure it out myself from the
documentation nor searching the list nor googling.
thanks!
robert.
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