R: Sorting Vectors or Data Frames by Other Vectors

sort_by {base}

R Documentation

Sorting Vectors or Data Frames by Other Vectors

Description

Generic function to sort an object in the order determined by one or more other objects, typically vectors. A method is defined for data frames to sort its rows (typically by one or more columns), and the default method handles vector-like objects.

Usage

sort_by(x, y, ...)

## Default S3 method:
sort_by(x, y, ...)

## S3 method for class 'data.frame'
sort_by(x, y, ...)

Arguments

x

An object to be sorted, typically a vector or data frame.

y

Variables to sort by.

For the default method, this can be a vector, or more generally any object that has a xtfrm method.

For the data.frame method, typically a formula specifying the variables to sort by. The formula can take the forms ~ g or ~ list(g) to sort by the variable g, or more generally the forms ~ g1 + ... + gk or ~ list(g1, ..., gk) to sort by the variables g1, ..., gk, using the later ones to resolve ties in the preceding ones. These variables are evaluated in the data frame x using the usual non-standard evaluation rules. If not a formula, y = g is equivalent to y = ~ g and y = list(g1, ..., gk) is equivalent to y = ~ list(g1, ..., gk). However, non-standard evaluation in x is not done in this case.

...

Additional arguments, typically passed on to order. These may include additional variables to sort by, as well as named arguments recognized by order.

Value

A sorted version of x. If x is a data frame, this means that the rows of x have been reordered to sort the variables specified in y.

Examples

mtcars$am
mtcars$mpg
with(mtcars, sort_by(mpg, am)) # group mpg by am

## data.frame method
sort_by(mtcars, runif(nrow(mtcars))) # random row permutation
sort_by(mtcars, list(mtcars$am, mtcars$mpg))

# formula interface
sort_by(mtcars, ~ am + mpg) |> subset(select = c(am, mpg))
sort_by.data.frame(mtcars, ~ list(am, -mpg)) |> subset(select = c(am, mpg))