List to dataframe

Question

I have the result of a select_multiple question stored in a list. That comes from a dataset collected with OpenDataKit

example <- list("a", c("b", "c"), c("d", "e", "f"), c(""))

In the example below for the record #4, there were no answers (meaning NA for all options).

I need to create a data frame from this list where each options from the select multiple would become a new variable. Each element of the list is de facto not of the same length.

The result should look like this:

variable | a   b    c    d     e    f
row1     | 1   0    0    0     0    0
row2     | 0   1    1    0     0    0 
row3     | 0   0    0    1     1    1
row4     | <NA> <NA><NA> <NA><NA> <NA>

I have found options with stri_list2matrix but that does not provide the expected results.

I tried as well

df <-data.frame( lNames <- rep(names(example), lapply(example, length)),
                  lVal <- unlist(example))

and got the same

arguments imply differing number of rows

Please help!

Thanks

Answer 1

You could use setNames, stack and dcast for that:

example <- list("a", c("b", "c"), c("d", "e", "f"), c(""))
example <- setNames(example, seq_along(example))

ex2 <- stack(example)
ex2[ex2$values=='','values'] <- NA

library(reshape2)
dcast(ex2, ind ~ values, fun.aggregate = length)

This will result in:

  ind a b c d e f NA
1   1 1 0 0 0 0 0  0
2   2 0 1 1 0 0 0  0
3   3 0 0 0 1 1 1  0
4   4 0 0 0 0 0 0  1