Return first or last element of an object

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Description

Return first or last element of an object. These functions are convenience wrappers for head(x, n=1, ...) and tail(x, n=1, ...).

Usage

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first(x, n=1, ...)
last(x, n=1, ...)

Arguments

x

data 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'.

...

arguments to be passed to or from other methods.

Value

An object (usually) like 'x' but generally smaller.

Author(s)

Gregory R. Warnes greg@warnes.net

See Also

head, tail, left, right

Examples

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## works for vectors..
v <- 1:10
first(v)
last(v)

## and for lists
l <- list(a=1, b=2, c=3)
first(l)
last(l)

## and data.frames
df <- data.frame(a=1:2, b=3:4, c=5:6)
first(df)
last(df)

## and matrixes
m <- as.matrix(df)
first(m)
last(m)

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