| nnzero {Matrix} | R Documentation |
Returns the number of non-zero values of a numeric-like R object, and
in particular an object x inheriting from class
Matrix.
nnzero(x, na.counted = NA)
x |
an R object, typically inheriting from class
|
na.counted |
a
For sparse matrices, you may often want to use |
the number of non zero entries in x (typically
integer).
Note that for a symmetric sparse matrix S (i.e., inheriting from
class symmetricMatrix), nnzero(S) is
typically twice the length(S@x).
signature(x = "ANY")the default method for
non-Matrix class objects, simply counts the
number 0s in x, counting NA's depending on
the na.counted argument, see above.
signature(x = "denseMatrix")conceptually the same as
for traditional matrix objects, care has to be taken
for "symmetricMatrix" objects.
signature(x = "diagonalMatrix"), and
signature(x = "indMatrix")fast simple methods for these
special "sparseMatrix" classes.
signature(x = "sparseMatrix")typically, the most
interesting method, also carefully taking
"symmetricMatrix" objects into account.
The Matrix class also has a
length method; typically, length(M) is much
larger than nnzero(M) for a sparse matrix M, and the latter is
a better indication of the size of M.
m <- Matrix(0+1:28, nrow = 4) m[-3,c(2,4:5,7)] <- m[ 3, 1:4] <- m[1:3, 6] <- 0 (mT <- as(m, "dgTMatrix")) nnzero(mT) (S <- crossprod(mT)) nnzero(S) str(S) # slots are smaller than nnzero() stopifnot(nnzero(S) == sum(as.matrix(S) != 0))# failed earlier data(KNex) M <- KNex$mm class(M) dim(M) length(M); stopifnot(length(M) == prod(dim(M))) nnzero(M) # more relevant than length ## the above are also visible from str(M)