CODEWITHSUNDEEP
rstring
rumtscho
rumtscho

Reputation: 2524

How to find an empty vector in a list?

I have a list where each element is a string. It happens that some of the elements are an empty character vector.

I want to get the indices of all those empty elements, but haven't found a syntax which delivers them. 

my.list <- lapply(c("I", "am", "not", "empty"), function(x) x)
my.list[[5]] <- character(0)
my.list[[6]] <- character(0)

All things I've tried (such as my.list=="", my.list==character(0)) deliver something entirely different. If I unlist the list, it suddenly misses the empty elements and is only 4 elements long.

What is the correct syntax to find the empty character vectors?

Upvotes: 1

Views: 1879

Answers (3)

Colonel Beauvel
Colonel Beauvel

Reputation: 31161

You can use R 3.2 version, from which lengths function is available:

which(!lengths(my.list))
[1] 5 6

Upvotes: 3

sebastian-c
sebastian-c

Reputation: 15395

You could use length:

lapply(my.list, length) == 0

For character vectors specifically, 

f <- function(v){

  is.character(v) && length(v) == 0

}

vapply(my.list, f, logical(1))

Mind you, Richard Telford's comment is the best answer to your question.

Upvotes: 1

jkt
jkt

Reputation: 946

which(sapply(my.list,length)==0)

Upvotes: 2

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