CODEWITHSUNDEEP
r
Japie
Japie

Reputation: 51

Is there a way to re-write a counter for-loop as a lapply/sapply/map function without using the " <<- " operator?

Is there a way to re-write the counter for-loop below using lapply/map (or sapply), but without using the "<<-" assignment operator?

I have a list of data frames (list_of_dfs) from which I need to determine the total number of rows contained in the entire list of data frames. The code below works fine, but I want to know if I can get away without using a for-loop and not using the scoping assignment operator "<<-" to count the total number of rows.

Counter for-loop:

count <- 0
for(df in list_of_dfs){
    count <- count + nrow(df)
}

The purrr::map function below does the trick, but I would like to avoid the "<<-" operator. purrr::walk, lapply and sapply gets to the same result. 

count <- 0
map(list_of_dfs, function(x){
    count <<- count + nrow(x)
})

It just seems sloppy...like some backyard workaround. Any advice would be appreciated.

Upvotes: 1

Views: 120

Answers (1)

akrun
akrun

Reputation: 887831

We an use sum

library(tidyverse)
map_int(list_of_dfs, nrow) %>%
     sum

Or with sapply

sum(sapply(list_of_dfs, nrow))

Upvotes: 3

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