Returns a sparse matrix with no “explicit zeroes”, i.e., all
FALSE entries are dropped from the explicitly indexed
drop0(x, tol = 0, is.Csparse = NA)
a Matrix, typically sparse, i.e., inheriting from
non-negative number to be used as tolerance for checking if an entry x[i,j] should be considered to be zero.
logical indicating prior knowledge about the
a Matrix like
x but with no explicit zeros, i.e.,
!any(x@x == 0), always inheriting from
When a sparse matrix is the result of matrix multiplications, you
may want to consider combining
see the example.
m <- spMatrix(10,20, i= 1:8, j=2:9, x = c(0:2,3:-1)) m drop0(m) ## A larger example: t5 <- new("dtCMatrix", Dim = c(5L, 5L), uplo = "L", x = c(10, 1, 3, 10, 1, 10, 1, 10, 10), i = c(0L,2L,4L, 1L, 3L,2L,4L, 3L, 4L), p = c(0L, 3L, 5L, 7:9)) TT <- kronecker(t5, kronecker(kronecker(t5,t5), t5)) IT <- solve(TT) I. <- TT %*% IT ; nnzero(I.) # 697 ( = 625 + 72 ) I.0 <- drop0(zapsmall(I.)) ## which actually can be more efficiently achieved by I.. <- drop0(I., tol = 1e-15) stopifnot(all(I.0 == Diagonal(625)), nnzero(I..) == 625)
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