CODEWITHSUNDEEP
r
lxcfuji
lxcfuji

Reputation: 339

change list into a data frame but keep the number of list order

I have a list with length of 14. Within each row, some of them are NULL value, and some of them have multiple numbers. This is the list:

> start_positions
[[1]]
NULL

[[2]]
NULL

[[3]]
NULL

[[4]]
[1] 1517

[[5]]
NULL

[[6]]
NULL

[[7]]
NULL

[[8]]
NULL

[[9]]
[1] 1410

[[10]]
[1] 5995

[[11]]
NULL

[[12]]
[1] 13880 24631

[[13]]
NULL

[[14]]
[1] 18622

I want to unlist it and delete those NULL values,but keep the number of the order of list, like this:

list    start_positions
4       1517
9       1410
10      5995
12      13880
12      24631
14      18622

I tried rbind() and do.call() with unlist(), but it just gave me only one column and rank it from 1. (I think I should name each one of the row? but I don't know how.)

Upvotes: 0

Views: 78

Answers (1)

A5C1D2H2I1M1N2O1R2T1
A5C1D2H2I1M1N2O1R2T1

Reputation: 193517

You'll get a warning because of the NULL values, but you can use stack:

myList <- list(NULL, NULL, 1, 2, NULL, c(3, 4)) ## Sample data
stack(setNames(myList, seq_along(myList)))
#   values ind
# 1      1   3
# 2      2   4
# 3      3   6
# 4      4   6
# Warning message:
# In stack.default(setNames(myList, seq_along(myList))) :
#   non-vector elements will be ignored

If you want to avoid the warning, you can subset the list after naming it:

names(myList) <- seq_along(myList)
stack(myList[!sapply(myList, is.null)])

Note that in any case stack needs names. In the first example, I added them "on the fly" using setNames, and in the second example, I added them directly.

Upvotes: 1

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