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]).

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()