Converting List to Data Frame

Question

I have a series of complex lists that I am trying to convert to data frame format in R. Each list will be converted to a data frame individually. Some of the lists have some values that are blank, making it hard to convert the list to a data frame.

I have tried lapply/ sapply to find the maximum length of the list and neither work. Additionally, using do.call and unlist does not give me the data in the format I want (it loses column titles and formats the table into three columns, rather than many columns). I found that the following code works on the first 5 lists:

max_list<-max(rapply(List, length))
df<-as.data.frame(rapply(List, function(x) 'length<-'(x, max_list), how="list"))

However, when I try to apply this in a loop for all of the lists, I get the following error.

Error in (function (..., row.names = NULL, check.rows = FALSE, check.names = TRUE,  : arguments imply differing number of rows: 3, 0

My ultimate goal is for the parts of the list that have missing values to be converted to "NA."

Is there anything I can add to this code to avoid the error? Or is there something else that I can do to convert those lists that have differing numbers of rows?

EDIT:

I can't post my exact code for the inputs online but the list is nested and is very complex.

Example input:

iter1 <- list(item1 = 1, item2 = "a",item3="b")
iter2 <- list(item1 = 2, item2 = "c")
List <- list(iter1 = iter1, iter2 = iter2)

Ideally, I'd like for this output as a data frame:

V1     V2     V3     V4     V5
1      a      b      2      c

As mentioned, I was able to get this result with the code above. But, I'm not sure why the code is failing when applied to more complex lists.

Hi. Could you provide an example of your input and the desired output? — Douglas Mesquita, Feb 07 '19 at 22:03
Please see [How to create a great reproducible example in R](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example) — Mako212, Feb 07 '19 at 22:05

score 1 · Accepted Answer · answered Feb 07 '19 at 23:09

1

You can use unlist and the argument recursive = T.

df <- data.frame(as.list(unlist(x = List, recursive = T, use.names = F)))
names(df) <- paste0("V", 1:ncol(df))
df

  V1 V2 V3 V4 V5
1  1  a  b  2  c

To make it easier to read:

library(dplyr)

unlist(x = List, recursive = T, use.names = F) %>%
  as.list() %>%
  data.frame() %>%
  setNames(nm = paste0("V", 1:ncol(.)))

  V1 V2 V3 V4 V5
1  1  a  b  2  c

answered Feb 07 '19 at 23:09

Douglas Mesquita

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Happy to help. If this answer or any other one solved your issue, please mark it as accepted. – Douglas Mesquita Feb 08 '19 at 15:05

Converting List to Data Frame

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