write.csv on a list of data frames

Question

I ma trying to save a number of data frames from a list in separate directory. something is wrong with my code:

lapply(na_s, function (x) write.csv(na_s[[x]],file = paste('/na_s_daily/',names (na_s[x]),'.csv',sep=""), row.names = F))

Error code:

Error in na_s[[x]] : invalid subscript type 'list'

Anybody can see what I am doing wrong?

Please make your question reproducible ... not knowing what na_s is makes this difficult to resolve. (Docs on minimal and reproducible questions.) — r2evans
– r2evans, Commented Feb 4, 2017 at 23:57

tatxif · Accepted Answer · 2017-02-05 21:24:30Z

2

The problem is that the input x is a number not the element of a list. Try

 lapply(1:length(na_sx),  function (x) write.csv(na_s[[x]],file = paste('./na_s_daily/','na_', names (na_s[x]),'.csv',sep=""), row.names = F))

Note that the above will also return a list of the data frames. So if you just need to save each element of the list as a data frame in your directory just do

for(x in 1:length(na_s)){
   write.csv(na_s[[x]],file = paste('./na_s_daily/','na_',names (na_s[x]),'.csv',sep=""), row.names = F)
}

edited Feb 5, 2017 at 21:24

answered Feb 5, 2017 at 0:19

tatxif

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5 Comments

m_c Over a year ago

I dont think that this solves my problem, and apply needs and argument to be passed on which object some function will be applied. which is a list na_s

tatxif Over a year ago

@m_c glad it worked! I updated the for loop too, if you just need to save each element. Please accept my answer if it helped you.

m_c Over a year ago

sounds, nice. you just need to fix the first answer, 1:N does not really work. :)

tatxif Over a year ago

@m_c if N = length(na_sx) then it works, but I changed it anyways as it looks nicer.

m_c Over a year ago

if I use 1:N, it gives me an error, because it sees it as object, which is not existing.

Jake Kaupp · Accepted Answer · 2017-02-05 17:56:07Z

2

If you want to use the names of the list, I would suggest using mapply. You also need to be sure the output directory exists before you use it, else you'll receive an error. I also changed paste to paste0 (which is paste(x, sep = "")).

na_s <- list("one" = mtcars, "two" = mtcars, "three" = mtcars)

mapply(function (x,y) write.csv(x, file = paste0('./na_s_daily/', y, '.csv'), row.names = F), na_s, names(na_s))

answered Feb 5, 2017 at 17:56

Jake Kaupp

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2 Comments

m_c Over a year ago

lapply(1:length(na_s), function (x) write.csv(na_s[[x]],file = paste('./na_s_monthly/','na_',names (na_s[x]),'.csv',sep=""), row.names = F))

worked for me.

Jake Kaupp Over a year ago

As it should. The differences are that the code in my answer doesn't need to reference list indices within the function.

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