R: Group Averages Over Level Combinations of Factors

ave {stats} | R Documentation

## Group Averages Over Level Combinations of Factors

### Description

Subsets of `x[]` are averaged, where each subset consist of those observations with the same factor levels.

### Usage

    ave(x, ..., FUN = mean)

### Arguments

`x` | A numeric.
`...` | Grouping variables, typically factors, all of the same `length` as `x`.
`FUN` | Function to apply for each factor level combination.

### Value

A numeric vector, say `y` of length `length(x)`. If `...` is `g1, g2`, e.g., `y[i]` is equal to `FUN(x[j]`, for all `j` with `g1[j] == g1[i]` and `g2[j] == g2[i])`.

### See Also

`mean`, `median`.

### Examples

    require(graphics)

    ave(1:3)  # no grouping -> grand mean

    attach(warpbreaks)
    ave(breaks, wool)
    ave(breaks, tension)
    ave(breaks, tension, FUN = function(x) mean(x, trim = 0.1))
    plot(breaks, main =
         "ave( Warpbreaks )  for   wool  x  tension  combinations")
    lines(ave(breaks, wool, tension              ), type = "s", col = "blue")
    lines(ave(breaks, wool, tension, FUN = median), type = "s", col = "green")
    legend(40, 70, c("mean", "median"), lty = 1,
          col = c("blue","green"), bg = "gray90")
    detach()

[Package stats version 3.1.2 Index]