funprog (Higher Order Functions)

http://www.johnmyleswhite.com/notebook/2010/09/23/higher-order-functions-in-r/
https://mitpress.mit.edu/sites/default/files/sicp/full-text/book/book.html

다른 Function을 argument로 사용하는 Function을 higher order function이라고 한다.

1. Reduce
2. Filter
3. Map
4. Find
5. Position
6. Negate

Reduce

Negate

List에서 NULL인 원소 제거하기

LL <- list( "sixx", NULL, NULL, c(21,32,11), TRUE, 16)
names(LL) <- seq_along(LL)

Filter(Negate(is.null), LL)

LL[sapply(LL, is.null)] <- NULL