创建由“from"和“to"向量定义的整数序列 [英] Create integer sequences defined by 'from' and 'to' vectors

问题描述

我有两个向量定义开始(从)索引和结束(到)索引:

I have two vectors which define start (from) indices and finish (to) indices:

Start = c(1, 10, 20)
Finish = c(9, 19, 30)

我想沿着两个向量创建一个所有 Start:Finish 序列的列表，即生成序列 Start[1]:Finish[1] (Start[1]:Finish[1]>1:9);Start[2]:Finish[2]，依此类推.

I want to create a list of all Start:Finish sequences along the two vectors, i.e. generate the sequences Start[1]:Finish[1] (1:9); Start[2]:Finish[2], and so on.

## [[1]]
## [1] 1 2 3 4 5 6 7 8 9
## 
## [[2]]
##  [1] 10 11 12 13 14 15 16 17 18 19
## 
## [[3]]
##  [1] 20 21 22 23 24 25 26 27 28 29 30

最好采用某种矢量化方式.'Start' 向量中的值将始终大于 'Finish' 向量中的相应元素.

Preferably in some vectorized way. The values in 'Start' vector will always be larger than the corresponding elements in 'Finish' vector.

推荐答案

只需使用mapply:

Start = c(1,10,20)
Finish = c(9,19,30)
mapply(":", Start, Finish)
## [[1]]
## [1] 1 2 3 4 5 6 7 8 9
## 
## [[2]]
##  [1] 10 11 12 13 14 15 16 17 18 19
## 
## [[3]]
##  [1] 20 21 22 23 24 25 26 27 28 29 30
## 

当然，您也可以使用 Vectorize，但这只是 mapply 的包装器.但是，Vectorize 不能与原始函数一起使用，因此您必须指定 seq.default 而不是 seq 或 seq.int.

You could, of course, also use Vectorize, but that's just a wrapper for mapply. However, Vectorize cannot be used with primitive functions, so you'll have to specify seq.default rather than seq, or seq.int.

示例:

Vectorize(seq.default)(Start, Finish)
## [[1]]
## [1] 1 2 3 4 5 6 7 8 9
## 
## [[2]]
##  [1] 10 11 12 13 14 15 16 17 18 19
## 
## [[3]]
##  [1] 20 21 22 23 24 25 26 27 28 29 30
## 

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