heplots (version 1.3-8)

# statList: Calculate statistics for levels of factors

## Description

`statList` provides a general method for calculating univariate or multivariate statistics for a matrix or data.frame stratified by one or more factors.

## Usage

`statList(X, factors, FUN, drop = FALSE, ...)colMeansList(X, factors, drop = FALSE, ...)covList(X, factors, drop = FALSE, ...)`

## Arguments

X

A matrix or data frame containing the variables to be summarized

factors

A vector, matrix or data frame containing the factors for which `X` is to be summarized. If `factors` is not specified, the result is calculated for all of the data in `X`.

FUN

A function to be applied to the pieces of `X`, as split by `factors`.

drop

Logical, indicating whether empty levels of `factors` are to be dropped from the result.

Other arguments, passed to `FUN`.

## Value

Returns a list of items corresponding to the unique elements in `factors`, or the interaction of `factors`. Each item is the result of applying `FUN` to that collection of rows of `X`. The items are named according to the levels in `factors`.

## Details

`statList` is the general function. `X` is first `split` by `factors`, and `FUN` is applied to the result.

`colMeansList` and `covList` are just calls to `statList` with the appropriate `FUN`.

## See Also

`colMeans`, `termMeans`

## Examples

```# NOT RUN {
# grand means
statList(iris[,1:4], FUN=colMeans)
# species means
statList(iris[,1:4], iris\$Species, FUN=colMeans)
# same
colMeansList(iris[,1:4], iris\$Species)

# var-cov matrices, by species
covList(iris[,1:4], iris\$Species)

# multiple factors
iris\$Dummy <- sample(c("Hi","Lo"),150, replace=TRUE)
colMeansList(iris[,1:4], iris[,5:6])

# }
```