Using rbind() to combine multiple data frames into one larger data.frame within lapply()

Question

I\'m using R-Studio 0.99.491 and R version 3.2.3 (2015-12-10). I\'m a relative newbie to R, and I\'d appreciate some help. I\'m doing a project where I\'m trying to use the

Answer 1

You can use map_df from purrr package instead of lapply, to directly have all results combined as a data frame.

map_df(files, read.table, skip = 3, header = TRUE, stringsAsFactors = FALSE)

Answer 2

Another option is fread from data.table

library(data.table)
rbindlist(lapply(files, fread, skip=3))

Answer 3

do.call() is your friend.

big.list.of.data.frames <- lapply(files, function(x){
    read.table(x, skip = 3, header = TRUE, stringsAsFactors = FALSE)
})

or more concisely (but less-tinkerable):

big.list.of.data.frames <- lapply(files, read.table, 
                                  skip = 3,header = TRUE,
                                  stringsAsFactors = FALSE)

Then:

big.data.frame <- do.call(rbind,big.list.of.data.frames)

This is a recommended way to do things because "growing" a data frame dynamically in R is painful. Slow and memory-expensive, because a new frame gets built at each iteration.