What are the rownames() and colnames() functions in R?

Overview

The rownames() and colnames() functions in R are used to obtain or set the names of the row and column of a matrix-like object, respectively.

Syntax

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

Parameter values

The rownames() and colnames() functions take the following parameter values:

• x: This is a matrix-like object that has at least two dimensions.
• do.Null: This takes a logical value. If FALSE and names are NULL, names are created.
• prefix: This represents the names that are created.
• value: This is a valid value for that component of dimnames(x) (that is, the values must be of the same dimension as the dimension of the matrix-like object). For a given array or matrix, this is either NULL or a character vector of non-zero length equal to the appropriate dimension.

Return value

The rownames() and colnames() functions both return a matrix object.

Code example

Code explanation

• Lines 2–3: We create the matrix objects col1 and col2.
• Line 6: We combine the matrix objects, using the cbind() function. Then we assign the result to a variable c.
• Line 10: We set names for the columns, using the colnames() function.
• Line 11: We set names for the rows, using the rownames() function.
• Line 13: We call the rownames() function on the variable c.
• Line 16: We print the variable c.
• Line 18: We obtain and print the column names of the matrix object, using the colnames() function.
• Line 22: We obtain and print the row names of the matrix object, using the colnames() function.