colnames
Column and Row Names

### Description

Extracts or replaces column and row names for matrix and array objects.

### Usage

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

### Arguments

x | a matrix or array object.
do.NULL | a logical value. If FALSE, the function returns the created names if the names for the column (colnames) or row (rownames) are NULL. If TRUE (the default), the function returns the names for the column (colnames) or row (rownames), if they exist; if they are NULL, it returns NULL.
prefix | a character string to use as a prefix when creating row or column names.

### Details

If object x has dimnames, then the first component is returned as row names and, if the second component exists, it is returned as column names.
If do.NULL = FALSE, you must specify new column names or row names using the prefix argument.
When you use value to set the column or row names, value must be a character vector.
If x is a matrix, the length of the character vector that you specify in value must match the number of columns for colnames or the number of rows for rownames present in the matrix x.
If x is a data frame, when you set the names, observe the following:

- column: the length of value must be less than or equal to the number of columns in x.
- row: value must contain unique values and must not contain missing values (NA). The length must be equal to the number of rows in x.

Value

rownames | returns the first element in the dimnames (if it exists) for the object.
colnames | returns the second element in the dimnames (if it exists) for the object.

If dimnames does not exist, or if the element in dimnames is NULL and do.NULL = FALSE, then a character vector of the appropriate length is created by prepending prefix to a sequence of integers beginning with "1".
See Also
dimnames, row.names, names
Examples

    m <- matrix(1:6, 3, 2)
    colnames(m)
    # NULL
    rownames(m)
    # NULL
    rownames(m) <- c("R1", "R2", "R3")
    # Generate names when there are none
    colnames(m, do.NULL = FALSE, prefix = "C")
    # [1] "C1" "C2"
    rownames(m) # R1, R2, R3
    # [1] "R1" "R2" "R3"

Package base version 6.1.5-18
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