CODEWITHSUNDEEP
r
Barnaby
Barnaby

Reputation: 1480

How to Group lists within a list of vectors

I have a list of 7 vectors, I would like to group the lists into 4 lists of vectors each. 

B2 <- list ( c (12 , 47 ,137 ,170), c(44 , 47 ,135, 170) , c(12 , 28 , 34 , 44 , 47 , 59 , 61 , 67 , 76 , 80 , 84 ,135, 148, 170) , c(44 , 47 , 84 ,135 ,170) , c(12 , 28 , 34 , 44 , 47 , 59 , 61 , 67 , 76 , 80 , 84 ,135, 148, 156, 159, 164, 170) , c(12 , 28 , 34 , 44 , 47 , 84 ,135 ,170) , c(12 , 28 , 44 , 47 , 84, 135, 170)) 

# I would like to create four groups (lists) as per the following index of consecutive list sequence)    

Subgroup <- c(2,4,5,7)

# Desired Output

  B2 <- list ( list ( c (12 , 47 ,137 ,170), c(44 , 47 ,135, 170)) , list ( c(12 , 28 , 34 , 44 , 47 , 59 , 61 , 67 , 76 , 80 , 84 ,135, 148, 170) , c(44 , 47 , 84 ,135 ,170)) , list ( c(12 , 28 , 34 , 44 , 47 , 59 , 61 , 67 , 76 , 80 , 84 ,135, 148, 156, 159, 164, 170)) , list ( c (12 , 28 , 34 , 44 , 47 , 84 ,135 ,170) , c(12 , 28 , 44 , 47 , 84, 135, 170)))

Upvotes: 3

Views: 88

Answers (3)

Carlos Cinelli
Carlos Cinelli

Reputation: 11597

Using split and rep:

split(B2, rep(1:length(Subgroup), diff(c(0, Subgroup))))

Upvotes: 1

akrun
akrun

Reputation: 887078

Here is an option using sequence

i1 <- sequence(Subgroup)
i2 <- !duplicated(i1)
res <- split(B2[i1[i2]],cumsum(c(TRUE,diff(i1)<0))[i2])
all.equal(res, Out, check.attributes=FALSE)
#[1] TRUE

Or as @Chris mentioned in the comments,

lst <- Map(`:`,  c(1,head(Subgroup,-1)+1), Subgroup)
lapply(lst, function(i) B2[i])

Upvotes: 1

marc1s
marc1s

Reputation: 779

Another option

rng = data.frame(1+c(0, head(Subgroup,-1)), Subgroup)
apply(rng, 1,function(x) B2[x[1]:x[2]])

Upvotes: 1

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