试试rep有可能就方便理解了
- mapply(rep, a$foo, a$bar)
- [[1]]
- [1] 0 0 0 0 0 0 0 0 0 0
- [[2]]
- [1] 1 1 1 1 1 1 1 1 1 1 1
- [[3]]
- [1] 2 2 2 2 2 2 2 2 2 2 2 2
- [[4]]
- [1] 3 3 3 3 3 3 3 3 3 3 3 3 3
- [[5]]
- [1] 4 4 4 4 4 4 4 4 4 4 4 4 4 4
- [[6]]
- [1] 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5
- [[7]]
- [1] 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6 6
- [[8]]
- [1] 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7 7
- [[9]]
- [1] 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8 8
- [[10]]
- [1] 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9
- [[11]]
- [1] 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10
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mean(x, trim = 0, na.rm = FALSE, ...); a$bar在报错中显然解释为 “trim"了
- mean(a$foo, a$bar)
- Error in mean.default(a$foo, a$bar) :
- 'trim' must be numeric of length one
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