创建具有固定增量的可变长度的多个序列？

Question

我想创建多个长度可变且序列之间有固定增量的序列。喜欢：

Seq.lengths<- c(2, 4, 2, 2, 2, 4)
increment <- 3

#Output should be a list like:

c(1:2, 5:8, 11:12, 15:16, 19:20, 23:26
)

我试过“for”循环，但它对我来说不太管用。

Answer 1

应该有一个更聪明的解决方案，但是使用 for 循环的方法看起来像 -

Seq.lengths<- c(2, 4, 2, 2, 2, 4)
increment <- 3
result <- 1:Seq.lengths[1]

for(i in Seq.lengths[-1]) {
  val <- result[length(result)] + increment
  result <- c(result, val:(val + i - 1))
}

result
#[1]  1  2  5  6  7  8 11 12 15 16 19 20 23 24 25 26

如果要将输出存储在列表中 -

Seq.lengths<- c(2, 4, 2, 2, 2, 4)
increment <- 3
result <- vector('list', length(Seq.lengths))
result[[1]] <- 1:Seq.lengths[1]

for(i in 2:length(Seq.lengths)){
  val <- result[[i-1]][length(result[[i-1]])] + increment
  result[[i]] <- val:(val + Seq.lengths[i] - 1)
}

result
#[[1]]
#[1] 1 2

#[[2]]
#[1] 5 6 7 8

#[[3]]
#[1] 11 12

#[[4]]
#[1] 15 16

#[[5]]
#[1] 19 20

#[[6]]
#[1] 23 24 25 26

Answer 2

因为你有 Seq.lenths，另一种选择可能是找到每个序列的开始

Seq.lengths  <- c(2, 4, 2, 2, 2, 4)
increment <- 3
Seq.i  <-  seq_along(Seq.lengths[-1])
Seq.start <- cumsum(c(1, Seq.lengths[Seq.i] + (increment - 1)))

然后使用Map和seq得到结果

Map(function (x, y) seq(from = x, length.out = y), x = Seq.start, y = Seq.lengths)
[[1]]
[1] 1 2

[[2]]
[1] 5 6 7 8

[[3]]
[1] 11 12

[[4]]
[1] 15 16

[[5]]
[1] 19 20

[[6]]
[1] 23 24 25 26

创建具有固定增量的可变长度的多个序列？

Creating multiple sequences with variable lengths with fixed increment?

r

sequence