search for: bookgroup

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2007 Dec 19
3
Aggregating by a grouping
Suppose I have: Book Value A 10 B 11 C 9 D 8 A 12 C 4 D 5 B 7 I want to summarize above not by Book but by groupings of Books as in (below) I have a list ... basic_map <- list(c("A",B"),c("C,D")) Big_names <- c("A1", "A2") Names(basic_map) <- big_names So I want to get : A1 40 A2 26 How do I use tapply AND the list to get my