utils (version 3.5.1)

head: Return the First or Last Part of an Object

Description

Returns the first or last parts of a vector, matrix, table, data frame or function. Since head() and tail() are generic functions, they may also have been extended to other classes.

Usage

head(x, …)
# S3 method for default
head(x, n = 6L, …)
# S3 method for data.frame
head(x, n = 6L, …)
# S3 method for matrix
head(x, n = 6L, …)
# S3 method for ftable
head(x, n = 6L, …)
# S3 method for table
head(x, n = 6L, …)
# S3 method for function
head(x, n = 6L, …)
tail(x, …)
# S3 method for default
tail(x, n = 6L, …)
# S3 method for data.frame
tail(x, n = 6L, …)
# S3 method for matrix
tail(x, n = 6L, addrownums = TRUE, …)
# S3 method for ftable
tail(x, n = 6L, addrownums = FALSE, …)
# S3 method for table
tail(x, n = 6L, addrownums = TRUE, …)
# S3 method for function
tail(x, n = 6L, …)

Arguments

x

an object

n

a single integer. If positive or zero, size for the resulting object: number of elements for a vector (including lists), rows for a matrix or data frame or lines for a function. If negative, all but the n last/first number of elements of x.

addrownums

if there are no row names, create them from the row numbers.

…

arguments to be passed to or from other methods.

Value

An object (usually) like x but generally smaller. For ftable objects x, a transformed format(x).

Details

For matrices, 2-dim tables and data frames, head() (tail()) returns the first (last) n rows when n >= 0 or all but the last (first) n rows when n < 0. head.matrix() and tail.matrix() are exported. For functions, the lines of the deparsed function are returned as character strings.

If a matrix has no row names, then tail() will add row names of the form "[n,]" to the result, so that it looks similar to the last lines of x when printed. Setting addrownums = FALSE suppresses this behaviour.

Examples

# NOT RUN {
head(letters)
head(letters, n = -6L)

head(freeny.x, n = 10L)
head(freeny.y)

tail(letters)
tail(letters, n = -6L)

tail(freeny.x)
tail(freeny.y)

tail(library)

head(stats::ftable(Titanic))
# }