row/colnames              package: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

