ave {stats}  R Documentation 
Subsets of x[]
are averaged, where each subset consist of those
observations with the same factor levels.
ave(x, ..., FUN = mean)
x 
A numeric. 
... 
Grouping variables, typically factors, all of the same

FUN 
Function to apply for each factor level combination. 
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])
.
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()