R - lapply - getting data frames back out of lists?

Question

I have the same problem as this guy: returning from list to data.frame after lapply

Whilst they solved his specific problem, no one actually answered his original question about how to get dataframes out of a list.

I have a list of data frames:

dfPreList = list(yearlyFunding, yearlyPubs, yearlyAuthors)

And I want to filter/replace etc on them all.

So my function is:

DoThis = function(x){
  filter(x, year >=2015 & year <=2018) %>% 
  replace(is.na(.), 0) %>%
  adorn_totals("row")

}

And I use lapply to run the function on them all like this:

a = lapply(dfPreList, DoThis)

As the other post stated, these data frames are now stuck in this list (a), and I need a for loop to get them out, which just cannot be the correct way of doing it.

This is my current working way of applying the function to the dataframes and then getting them out:

dfPreList = list(yearlyFunding, yearlyPubs, yearlyAuthors)
dfPreListstr= list('yearlyFunding', 'yearlyPubs', 'yearlyAuthors')

DoThis = function(x){
  filter(x, year >=2015 & year <=2018) %>% 
  replace(is.na(.), 0) %>%
  adorn_totals("row")

}

a = lapply(dfPreList, DoThis)

for( i in seq_along(dfPreList)){

  assign(dfPreListstr[[i]], as.data.frame(a[i]))

}

Is there a way of doing this without having to rely on for loops and string names of the dataframes? I.e. a one-liner with the lapply?

Many thanks for your help

Ronak Shah · Accepted Answer · 2020-02-05T13:00:53.337

2

You can assign names to the list and then use list2env.

dfPreList = list(yearlyFunding, yearlyPubs, yearlyAuthors)
a = lapply(dfPreList, DoThis) 
names(a) <- c('yearlyFunding', 'yearlyPubs', 'yearlyAuthors')
list2env(a, .GlobalEnv)

edited Feb 05 '20 at 13:00

answered Feb 05 '20 at 12:54

Ronak Shah

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Thanks. However. lapply returns a list of lists, and I am a bit confused by your code? i.e. I don't see where the 'a = lapply(dfPreList, DoThis)' comes in? i.e. I want to unwrap 'a' which has the result of lapply stored as lists. Thank you! – Nicholas Feb 05 '20 at 12:59
1

@ScoutEU Okay. Updated the answer. Can you check now? – Ronak Shah Feb 05 '20 at 13:01
Thank you so much, this is perfect :) – Nicholas Feb 05 '20 at 13:09

score 1 · Answer 2 · answered Feb 05 '20 at 13:45

Another way would be to unlist the list, then convert the content into data frame.

dfPreList = list(yearlyFunding, yearlyPubs, yearlyAuthors)
a = lapply(dfPreList, DoThis)
names(a) <- c('yearlyFunding', 'yearlyPubs', 'yearlyAuthors')

yearlyFunding <- data.frame(matrix(unlist(a$yearlyFunding), nrow= nrow(yearlyFunding), ncol= ncol(yearlyFunding)))
yearlyPubs <- data.frame(matrix(unlist(a$yearlyPubs), nrow= nrow(yearlyPubs), ncol= ncol(yearlyPubs)))
yearlyAuthors <- data.frame(matrix(unlist(a$yearlyAuthors), nrow= nrow(yearlyAuthors), ncol= ncol(yearlyAuthors)))

Since unlist function returns a vector, we first generate a matrix, then convert it to data frame.

Hey phago, whilst useful, I have made my post purposely short so have missed out about 30 data frames. I wanted an iterative process so I don't have to type out 30 lines of un-listing. Thank you though! — Nicholas, Feb 05 '20 at 13:50

R - lapply - getting data frames back out of lists?

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