CODEWITHSUNDEEP
rfunctionlapply
user1491868
user1491868

Reputation: 326

R lapply different function to each element of list

I have a list (in R) where the elements are different data types, e.g., the first element is numeric and the second element is character. I would like to apply a different function to each element. For example, in the code below I try to apply the sum function only to the first element and the length function only to the second element. Is there a way to apply a different function to each element of a list (without breaking up the list)?

data <- list(
  A = rnorm(10),
  B = letters[1:10]
)

lapply(data, list(sum, length))

mapply(function(x) sum, length, data)

Upvotes: 10

Views: 2221

Answers (2)

Frank
Frank

Reputation: 66819

I would do something like

sapply( data, function(x) (if(is.character(x)) length else sum)(x) )

Complicated alternatives. If speed is a concern, vapply should be faster:

vapply( data, function(x) (if(is.character(x)) length else sum)(x), numeric(1) )

If you need to use length many times, it's fast to use lengths (available in R 3.2.0+):

res          <- lengths(data)
get_sum      <- !sapply(data,is.character)
res[get_sum] <- sapply(data[get_sum],sum)

Upvotes: 6

MrFlick
MrFlick

Reputation: 206232

How about

mapply(function(a,b) b(a), data, list(sum, length))

Notice that we put the functions in mapply in a list as well.

Upvotes: 17

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