将数字向量转换为区间列表

Question

I have the following vector

x <- c(1,3,4,5,8,9,10,13)

I wish to transform it into a set of intervals:

iwant <-  list(1, c(3,5), c(8,10), 13)
iwant
#> [[1]]
#> [1] 1
#> 
#> [[2]]
#> [1] 3 5
#> 
#> [[3]]
#> [1]  8 10
#> 
#> [[4]]
#> [1] 13

is there an easy way to tranform x such into groups of interval ranges in R or with Rcpp (real x vector may be have up to ~ 80M values) that I've completely missed? If not can someone point me to an algorithm I can't seem to figure it out.

Answer 1

It is not clear waht you are looking to do ,but here how you can reproduce the expected result:

lapply(split(x,c(0,cumsum(diff(x)!=1))),
       function(y)if(length(y)>2) c(y[1],tail(y,1))else y)


$`0`
[1] 1

$`1`
[1] 3 5

$`2`
[1]  8 10

$`3`
[1] 13

Answer 2

I'm not exactly sure how you're defining an instance of an interval but here's one way using the IRanges package ( installation instructions ). It has really good documentation.

require(IRanges)
reduce(IRanges(x, x))
# IRanges of length 4
#     start end width
# [1]     1   1     1
# [2]     3   5     3
# [3]     8  10     3
# [4]    13  13     1