[R] what does this syntax mean?

[Uwe Ligges]

ronggui wrote:

> 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?

See ?split and ?lapply.

x is grouped by g, FUNis applied on each group and assigned back to the 
original values.

Uwe Ligges


> thank you!
> 
> 
>