[R] what does this syntax mean?

[ronggui]

i study the code of function ave,but i can understand one line of the syntax.

> ave
function (x, ..., FUN = mean)
{
    n <- length(list(...))
    if (n) {
        g <- interaction(...)
        split(x, g) <- lapply(split(x, g), FUN)
    }
    else x[] <- FUN(x)
    x
}

my question is : what does "split(x, g) <- lapply(split(x, g), FUN)" mean?

thank you!



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Department of Sociology
Fudan University,Shanghai
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