row.names {base}R Documentation

Get and Set Row Names for Data Frames

Description

All data frames have a row names attribute, a character vector of length the number of rows with no duplicates nor missing values.

For convenience, these are generic functions for which users can write other methods, and there are default methods for arrays. The description here is for the data.frame method.

Usage

row.names(x)
row.names(x) <- value

Arguments

x object of class "data.frame", or any other class for which a method has been defined.
value an object to be coerced to character unless an integer vector. It should have (after coercion) the same length as the number of rows of x with no duplicated nor missing values. NULL is also allowed: see Details.

Details

A data frame has (by definition) a vector of row names which has length the number of rows in the data frame, and contains neither missing nor duplicated values.

Prior to R 2.4.0, row names were character. As from R 2.4.0, they are allowed to be integer or character, but for backwards compatibility row.names will always return a character vector. (Use attr(x, "row.names") if you need the actual value.)

Using NULL for the value resets the row names to seq_len(nrow(x)).

Value

row.names returns a character vector.
row.names<- returns a data frame with the row names changed.

Note

row.names is similar to rownames for arrays, and it has a method that calls rownames for an array argument.

Row names of the form 1:n for n > 2 are stored internally in a compact form, which might be seen from C code or by deparsing but never via row.names or attr(x, "row.names").

References

Chambers, J. M. (1992) Data for models. Chapter 3 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.

See Also

data.frame, rownames, names.


[Package base version 2.4.1 Index]