[R] Convert list of data frames to one data frame

[Sarah Goslee]

Hi,

It isn't super clear to me what you're after. Is this what you intend?

> dfbycol(employees4BList)
  first1 last1 first2 last2 first3 last3
1     Al Jones   <NA>  <NA>   <NA>  <NA>
2     Al Jones   Barb Smith   <NA>  <NA>
3     Al Jones   Barb Smith  Carol Adams
4     Al Jones   <NA>  <NA>   <NA>  <NA>
>
> dfbycol(employees4List)
  first1  last1  first2 last2 first3 last3
1     Al  Jones    <NA>  <NA>   <NA>  <NA>
2    Al2  Jones    Barb Smith   <NA>  <NA>
3    Al3  Jones Barbara Smith  Carol Adams
4     Al Jones2    <NA>  <NA>   <NA>  <NA>


If so:

employees4BList = list(
data.frame(first1 = "Al", second1 = "Jones"),
data.frame(first1 = c("Al", "Barb"), second1 = c("Jones", "Smith")),
data.frame(first1 = c("Al", "Barb", "Carol"), second1 = c("Jones",
"Smith", "Adams")),
data.frame(first1 = ("Al"), second1 = "Jones"))

employees4List = list(
data.frame(first1 = ("Al"), second1 = "Jones"),
data.frame(first2 = c("Al2", "Barb"), second2 = c("Jones", "Smith")),
data.frame(first3 = c("Al3", "Barbara", "Carol"), second3 = c("Jones",
"Smith", "Adams")),
data.frame(first4 = ("Al"), second4 = "Jones2"))

###

dfbycol <- function(x) {
  x <- lapply(x, function(y)as.vector(t(as.matrix(y))))
  x <- lapply(x, function(y){length(y) <- max(sapply(x, length)); y})
  x <- do.call(rbind, x)
  x <- data.frame(x, stringsAsFactors=FALSE)
  colnames(x) <- paste0(c("first", "last"), rep(seq(1, ncol(x)/2), each=2))
  x
}

###

dfbycol(employees4BList)

dfbycol(employees4List)

On Fri, Jun 29, 2018 at 2:36 AM, Ira Sharenow via R-help
<r-help using r-project.org> wrote:
> I have a list of data frames which I would like to combine into one data
> frame doing something like rbind. I wish to combine in column order and
> not by names. However, there are issues.
>
> The number of columns is not the same for each data frame. This is an
> intermediate step to a problem and the number of columns could be
> 2,4,6,8,or10. There might be a few thousand data frames. Another problem
> is that the names of the columns produced by the first step are garbage.
>
> Below is a method that I obtained by asking a question on stack
> overflow. Unfortunately, my example was not general enough. The code
> below works for the simple case where the names of the people are
> consistent. It does not work when the names are realistically not the same.
>
> https://stackoverflow.com/questions/50807970/converting-a-list-of-data-frames-not-a-simple-rbind-second-row-to-new-columns/50809432#50809432
>
>
> Please note that the lapply step sets things up except for the column
> name issue. If I could figure out a way to change the column names, then
> the bind_rows step will, I believe, work.
>
> So I really have two questions. How to change all column names of all
> the data frames and then how to solve the original problem.
>
> # The non general case works fine. It produces one data frame and I can
> then change the column names to
>
> # c("first1", "last1","first2", "last2","first3", "last3",)
>
> #Non general easy case
>
> employees4BList = list(data.frame(first1 = "Al", second1 = "Jones"),
>
> data.frame(first1 = c("Al", "Barb"), second1 = c("Jones", "Smith")),
>
> data.frame(first1 = c("Al", "Barb", "Carol"), second1 = c("Jones",
> "Smith", "Adams")),
>
> data.frame(first1 = ("Al"), second1 = "Jones"))
>
> employees4BList
>
> bind_rows(lapply(employees4BList, function(x) rbind.data.frame(c(t(x)))))
>
> # This produces a nice list of data frames, except for the names
>
> lapply(employees4BList, function(x) rbind.data.frame(c(t(x))))
>
> # This list is a disaster. I am looking for a solution that works in
> this case.
>
> employees4List = list(data.frame(first1 = ("Al"), second1 = "Jones"),
>
> data.frame(first2 = c("Al2", "Barb"), second2 = c("Jones", "Smith")),
>
> data.frame(first3 = c("Al3", "Barbara", "Carol"), second3 = c("Jones",
> "Smith", "Adams")),
>
> data.frame(first4 = ("Al"), second4 = "Jones2"))
>
>   bind_rows(lapply(employees4List, function(x) rbind.data.frame(c(t(x)))))
>
> Thanks.
>
> Ira
>

-- 
Sarah Goslee
http://www.functionaldiversity.org