firstlastobs {doBy}

Locate the index of the first/last unique value

Description

Locate the index of the first/last unique value in i) a vector or of a variable in a data frame.

Usage

lastobs(x, ...)

firstobs(x, ...)

## Default S3 method:
lastobs(x, ...)

## Default S3 method:
firstobs(x, ...)

## S3 method for class 'formula'
lastobs(formula, data = parent.frame(), ...)

## S3 method for class 'formula'
firstobs(formula, data = parent.frame(), ...)

Arguments

x

A vector

...

Currently not used

formula

A formula (only the first term is used, see 'details').

data

A data frame

Details

If writing ~a + b + c as formula, then only a is considered.

Value

A vector.

Author(s)

Søren Højsgaard, [e-mail]

Examples

x <- c(rep(1, 5), rep(2, 3), rep(3, 7), rep(1, 4))
firstobs(x)
lastobs(x)
data(dietox)
firstobs(~Pig, data=dietox)
lastobs(~Pig, data=dietox)