CODEWITHSUNDEEP
regexrparsingstrsplit
FooBar
FooBar

Reputation: 16478

Why does strsplit return a list

Consider

text <- "who let the dogs out"
fooo <- strsplit(text, " ")
fooo
[[1]]
[1] "who"  "let"  "the"  "dogs" "out"

the output of strsplit is a list. The list's first element then is a vector, that contains the words above.

Why does the function behave that way? Is there any case in which it would return a list with more than one element?

And I can access the words using

fooo[[1]][1]
[1] "who"

, but is there no simpler way?

Upvotes: 8

Views: 3989

Answers (1)

nrussell
nrussell

Reputation: 18602

To your first question, one reason that comes to mind is so that it can keep different length result vectors in the same object, since it is vectorized over x:

text <- "who let the dogs out"
vtext <- c(text, "who let the")
##
> strsplit(text, " ")
[[1]]
[1] "who"  "let"  "the"  "dogs" "out" 

> strsplit(vtext, " ")
[[1]]
[1] "who"  "let"  "the"  "dogs" "out" 

[[2]]
[1] "who" "let" "the"

If this were to be returned as a data.frame, matrix, etc... instead of a list, it would have to be padded with additional elements.

Upvotes: 11

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