Write to files in R using a loop

Question

I have several variables as follow:

cats <- "some long text with info"
dogs <- "some long text with info"
fish <- "some long text with info"
....

and I manually write the content of these variables into a text file:

write.table(cats, "info/cats.txt", sep="\t")
write.table(dogs, "info/dogs.txt", sep="\t")
....

I read the answer to this question and tried to write a loop to automatically write the files.

So I created a list:

lst <<- list(cats, dogs,fish, ....)

and then iterated through the list:

for(i in seq_along(lst)) {
    write.table(lst[[i]], paste(names(lst)[i], ".txt", sep = ""), 
               col.names = FALSE, row.names = FALSE,  sep = "\t")
}

but the output of the above iteration is one text file called .txt and it contains the content of the last variable in the list.

any idea why the above loop doesn't work as expected?

Yes -- you did not name your list. Equivalently, paste0(NULL, ".txt") — nrussell
– nrussell, Commented Mar 8, 2016 at 20:07

Hong Ooi · Accepted Answer · 2016-03-08 20:06:10Z

6

Note the following:

> cats <- "some long text with info"
> dogs <- "some long text with info"
> fish <- "some long text with info"
> lst <- list(cats, dogs,fish)  # not <<-
> names(lst)
NULL

When you created your list, you didn't give it any names, so your loop doesn't have anything to work with. A fix:

> names(lst) <- c("cats", "dogs", "fish")

answered Mar 8, 2016 at 20:06

Hong Ooi

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4 Comments

Rain Man Over a year ago

thanks, I thought the name is automatically selected from the list

Gregor Thomas Over a year ago

Named arguments will become list names, e.g., list = list(cats = cats, name_of_dog_item = dogs, fish_here = fish) will have names "cats", "name_of_dog_item", etc.

nrussell Over a year ago

Alternatively, mget will name your list automatically: mget(c("cats", "dogs", "fish")).

Rain Man Over a year ago

@HongOoi is it possible to create a loop for the first part too?

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