by(data, INDICES, FUN, ..., simplify = TRUE)
A data frame is split by row into data frames subsetted by the values of one or more factors, and function
FUN is applied to each subset in turn.
data will be coerced to a data frame by the default method, but if this results in a 1-column data frame, the objects passed to
FUN are dropped to a subsets of that column.
An object of class
"by", giving the results for each subset. This is always a list if
simplify is false, otherwise a list or array (see
require(stats) by(warpbreaks[, 1:2], warpbreaks[,"tension"], summary) by(warpbreaks[, 1], warpbreaks[, -1], summary) by(warpbreaks, warpbreaks[,"tension"], function(x) lm(breaks ~ wool, data = x)) ## now suppose we want to extract the coefficients by group tmp <- with(warpbreaks, by(warpbreaks, tension, function(x) lm(breaks ~ wool, data = x))) sapply(tmp, coef)
Documentation reproduced from R 3.0.2. License: GPL-2.