ave                   package:base                   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:

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

     data(warpbreaks)
     attach(warpbreaks)
     ave(breaks, wool)
     ave(breaks, tension)
     ave(breaks, tension, FUN = function(x)mean(x, trim=.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()

