How to flatten a list of lists?

Here's another method that worked for my list of lists.

df <- as.data.frame(do.call(rbind, lapply(foolist, as.data.frame)))

Or take a look at new functions in tidyr which work well.

rectangle a nested list into a tidy tibble

rectangling

    lst <-  list(
      list(
        age = 23,
        gender = "Male",
        city = "Sydney"
      ),
      list(
        age = 21,
        gender = "Female",
        city = "Cairns"
      )
    )
      
    tib <- tibble(lst)  %>% 
      unnest_wider(lst)

df <- as.data.frame(tib)

Here's a more general solution for when lists are nested multiple times and the amount of nesting differs between elements of the lists:

 flattenlist <- function(x){  
  morelists <- sapply(x, function(xprime) class(xprime)[1]=="list")
  out <- c(x[!morelists], unlist(x[morelists], recursive=FALSE))
  if(sum(morelists)){ 
    Recall(out)
  }else{
    return(out)
  }
}

I expect that unlist(foolist) will help you. It has an option recursive which is TRUE by default.

So unlist(foolist, recursive = FALSE) will return the list of the documents, and then you can combine them by:

do.call(c, unlist(foolist, recursive=FALSE))

do.call just applies the function c to the elements of the obtained list