stats (version 3.3)

# reorder.default: Reorder Levels of a Factor

## Description

`reorder` is a generic function. The `"default"` method treats its first argument as a categorical variable, and reorders its levels based on the values of a second variable, usually numeric.

## Usage

```reorder(x, ...)## S3 method for class 'default':
reorder(x, X, FUN = mean, \dots,
order = is.ordered(x))```

## Arguments

x
An atomic vector, usually a factor (possibly ordered). The vector is treated as a categorical variable whose levels will be reordered. If `x` is not a factor, its unique values will be used as the implicit levels.
X
a vector of the same length as `x`, whose subset of values for each unique level of `x` determines the eventual order of that level.
FUN
a function whose first argument is a vector and returns a scalar, to be applied to each subset of `X` determined by the levels of `x`.
...
optional: extra arguments supplied to `FUN`
order
logical, whether return value will be an ordered factor rather than a factor.

## Value

• A factor or an ordered factor (depending on the value of `order`), with the order of the levels determined by `FUN` applied to `X` grouped by `x`. The levels are ordered such that the values returned by `FUN` are in increasing order. Empty levels will be dropped.

Additionally, the values of `FUN` applied to the subsets of `X` (in the original order of the levels of `x`) is returned as the `"scores"` attribute.

## See Also

`reorder.dendrogram`, `levels`, `relevel`.

## Examples

```require(graphics)

bymedian <- with(InsectSprays, reorder(spray, count, median))
boxplot(count ~ bymedian, data = InsectSprays,
xlab = "Type of spray", ylab = "Insect count",
main = "InsectSprays data", varwidth = TRUE,
col = "lightgray")```