row/colnames {base}R Documentation

Row and Column Names


Retrieve or set the row or column names of a matrix-like object.


rownames(x, do.NULL = TRUE, prefix = "row")
rownames(x) <- value

colnames(x, do.NULL = TRUE, prefix = "col")
colnames(x) <- value


x a matrix-like R object, with at least two dimensions for colnames.
do.NULL logical. Should this create names if they are NULL?
prefix for created names.
value a valid value for that component of dimnames(x). For a matrix or array this is either NULL or a character vector of length the appropriate dimension.


The extractor functions try to do something sensible for any matrix-like object x. If the object has dimnames the first component is used as the row names, and the second component (if any) is used for the col names. For a data frame, rownames and colnames are equivalent to row.names and names respectively.

If do.NULL is FALSE, a character vector (of length NROW(x) or NCOL(x)) is returned in any case, prepending prefix to simple numbers, if there are no dimnames or the corresponding component of the dimnames is NULL.

For a data frame, value for rownames should be a character vector of unique names, and for colnames a character vector of unique syntactically-valid names. (Note: uniqueness and validity are not enforced.)

See Also

dimnames, case.names, variable.names.


m0 <- matrix(NA, 4, 0)

m2 <- cbind(1,1:4)
colnames(m2, do.NULL = FALSE)
colnames(m2) <- c("x","Y")
rownames(m2) <- rownames(m2, do.NULL = FALSE, prefix = "Obs.")

[Package base version 2.1.0 Index]