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
Matrix or numeric . |
na.counted |
a logical describing how
NA s should be counted. There are three possible
settings for na.counted :
na.counted = TRUE .
|
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)
.
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)