i need build function traverses lists , sublists recursively , convert data.frame. let's have list that
from <- list(id="12345678", name="gabriele") message <- "the quick fox" comments <- list(list(name="mickey", comment="hello world!"), list(name="donald", message="world...hello!")) big.list <- list(from, message, comments) i need convert in form of data.frame schema
from_id, from_name, message, comments_name, comments_message (in other words, flattening sublists)
the problem don't know in advance fields have in lists , i've not (for example, posts may miss comments section altogether)
tnx in advance help!
below quick trial. if big.list has names, can taken column names.
the inner do.call() flattens sub-list while outer 1 converts data frame.
lst1 <- list(from = list(id="12345678", name="gabriele"),message = "the quick fox", comments = list(list(name="mickey", comment="hello world!"), list(name="donald", message="world...hello!"))) lst2 <- list(from = list(id="12345678", name="gabriele"),message = "the quick fox", comments = list(list(name="mickey", comment="hello world!"))) lst3 <- list(from = list(id="12345678", name="gabriele"),message = "the quick fox") df1 <- do.call(data.frame, do.call(c, lst1)) df2 <- do.call(data.frame, do.call(c, lst2)) df3 <- do.call(data.frame, do.call(c, lst3)) df1 #from.id from.name message comments1.name comments1.comment comments2.name comments2.message #1 12345678 gabriele quick fox mickey hello world! donald world...hello! df2 #from.id from.name message comments.name comments.comment #1 12345678 gabriele quick fox mickey hello world! df3 #from.id from.name message #1 12345678 gabriele quick fox @ gabriele b
below clumsy working solution. others may post better one.
from <- list(id="12345678", name="gabriele") message <- "the quick fox" comments <- list(list(name="mickey", comment="hello world!"), list(name="donald", message="world...hello!")) big.list <- list(from = from, message = message, comments = comments) big.list1 <- list(from = from, message = message) join <- function(lst) { if(length(lst$comments) < 1) { bnd <- data.frame(id = unlist(lst$from)[1], name = unlist(lst$from)[2], lst$message) bnd$cmt.name <- "na" bnd$comment <- "na" bnd } else { bnd <- do.call(rbind, lapply(1:length(lst$comments), function(x) { id <- unlist(lst$from)[1] name <- unlist(lst$from)[2] data.frame(id = id, name = name, lst$message) })) bnd <- cbind(bnd, do.call(rbind, lst$comments)) names(bnd) <- c("id", "name", "message", "cmt.name", "comment") bnd } } join(big.list) #id name message cmt.name comment #id 12345678 gabriele quick fox mickey hello world! #id1 12345678 gabriele quick fox donald world...hello! join(big.list1) #id name lst.message cmt.name comment #id 12345678 gabriele quick fox na na 
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