The Number of Rows/Columns of an Array

Description

nrow and ncol return the number of rows or columns present in x. NCOL and NROW do the same treating a vector as 1-column matrix, even a 0-length vector, compatibly with as.matrix() or cbind(), see the example.

Usage

nrow(x)
ncol(x)
NCOL(x)
NROW(x)

Arguments

Value

an integer of length 1 or NULL, the latter only for ncol and nrow.

References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole (ncol and nrow.)

See Also

dim which returns all dimensions; array, matrix.

Examples

ma <- matrix(1:12, 3, 4)
nrow(ma)   # 3
ncol(ma)   # 4

ncol(array(1:24, dim = 2:4)) # 3, the second dimension
NCOL(1:12) # 1
NROW(1:12) # 12

## as.matrix() produces 1-column matrices from 0-length vectors,
## and so does cbind() :
dim(as.matrix(numeric())) # 0 1
dim(    cbind(numeric())) # ditto
## consequently, NCOL(.) gives 1, too :
NCOL(numeric()) # 1 and hence
NCOL(NULL)      # 1