row/colnames {base}

R Documentation

Row and Column Names

Description

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

Usage

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

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

Arguments

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 non-zero length equal to the appropriate dimension.

Details

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 column names. For a data frame, rownames and colnames eventually call row.names and names respectively, but the latter are preferred.

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.

The replacement methods for arrays/matrices coerce vector and factor values of value to character, but do not dispatch methods for as.character.

For a data frame, value for rownames should be a character vector of non-duplicated and non-missing names (this is enforced), and for colnames a character vector of (preferably) unique syntactically-valid names. In both cases, value will be coerced by as.character, and setting colnames will convert the row names to character.

See Also

dimnames, case.names, variable.names.

Examples

m0 <- matrix(NA, 4, 0)
rownames(m0)

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

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