Return the First or Last Part of an Object

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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

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head(x, ...)
## Default S3 method:
head(x, n = 6L, ...)
## S3 method for class 'data.frame'
head(x, n = 6L, ...)
## S3 method for class 'matrix'
head(x, n = 6L, ...)
## S3 method for class 'ftable'
head(x, n = 6L, ...)
## S3 method for class 'table'
head(x, n = 6L, ...)
## S3 method for class 'function'
head(x, n = 6L, ...)

tail(x, ...)
## Default S3 method:
tail(x, n = 6L, ...)
## S3 method for class 'data.frame'
tail(x, n = 6L, ...)
## S3 method for class 'matrix'
tail(x, n = 6L, addrownums = TRUE, ...)
## S3 method for class 'ftable'
tail(x, n = 6L, addrownums = FALSE, ...)
## S3 method for class 'table'
tail(x, n = 6L, addrownums = TRUE, ...)
## S3 method for class 'function'
tail(x, n = 6L, ...)

Arguments

x

an object

n

a single integer. If positive, 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.

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.

Value

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

Author(s)

Patrick Burns, improved and corrected by R-Core. Negative argument added by Vincent Goulet.

Examples

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