Closes #1132. setDF converts list of equal lengths to DF by ref.

R/data.table.R

@@ -2374,13 +2374,32 @@ address <- function(x) .Call(Caddress, eval(substitute(x), parent.frame()))
 ":=" <- function(...) stop('Check that is.data.table(DT) == TRUE. Otherwise, := and `:=`(...) are defined for use in j, once only and in particular ways. See help(":=").')
 
 setDF <- function(x) {
- if (!is.data.table(x) && !is.data.frame(x)) stop("setDF only accepts data.table or data.frame as input")
+ if (!is.list(x)) stop("setDF only accepts data.table, data.frame or list of equal length as input")
  if (is.data.table(x)) {
  # copied from as.data.frame.data.table
  setattr(x, "row.names", .set_row_names(nrow(x)))
  setattr(x, "class", "data.frame")
  setattr(x, "sorted", NULL)
  setattr(x, ".internal.selfref", NULL)
+ } else if (is.data.frame(x)) {
+ x
+ } else {
+ n = vapply(x, length, 0L)
+ mn = max(n)
+ if (any(n<mn))
+ stop("All elements in argument 'x' to 'setDF' must be of same length")
+ xn = names(x)
+ if (is.null(xn)) {
+ setattr(x, "names", paste("V",seq_len(length(x)),sep=""))
+ } else {
+ idx = xn %chin% ""
+ if (any(idx)) {
+ xn[idx] = paste("V", seq_along(which(idx)), sep="")
+ setattr(x, "names", xn)
+ }
+ }
+ setattr(x,"row.names",.set_row_names(max(n)))
+ setattr(x,"class","data.frame")
  }
  invisible(x)
 }

README.md

@@ -60,6 +60,8 @@
 
  20. `setDT` gains a `key` argument so that `setDT(X, key="a")` would convert `X` to a `data.table` by reference *and* key by the columns specified. Closes [#1121](https:/Rdatatable/data.table/issues/1121).
 
+ 21. `setDF` also converts `list` of equal length to `data.frame` by reference now. Closes [#1132](https:/Rdatatable/data.table/issues/1132).
+
 #### BUG FIXES
 
  1. `if (TRUE) DT[,LHS:=RHS]` no longer prints, [#869](https:/Rdatatable/data.table/issues/869). Tests added. To get this to work we've had to live with one downside: if a `:=` is used inside a function with no `DT[]` before the end of the function, then the next time `DT` is typed at the prompt, nothing will be printed. A repeated `DT` will print. To avoid this: include a `DT[]` after the last `:=` in your function. If that is not possible (e.g., it's not a function you can change) then `print(DT)` and `DT[]` at the prompt are guaranteed to print. As before, adding an extra `[]` on the end of `:=` query is a recommended idiom to update and then print; e.g. `> DT[,foo:=3L][]`. Thanks to Jureiss for reporting.

inst/tests/tests.Rraw

@@ -4724,6 +4724,13 @@ test(1305.1, setDF(DT), data.frame(x=1:5, y=6:10))
 # setDF should return if input is data.frame, not error.
 df <- data.frame(x=1:5, y=6:10)
 test(1305.2, setDF(df), df) # setDF works on data.frame
+# setDF also works on lists with equal lengths, #1132
+df <- list(a=1:5, b=6:10)
+test(1305.3, data.frame(df), setDF(df))
+df <- list(1:5, 6:10)
+test(1305.4, setDF(as.data.table(df)), setDF(df))
+test(1305.5, setDF(1:5), error="setDF only accepts")
+test(1305.6, setDF(list(1, 2:3)), error="All elements in argument")
 
 # .SD retains as much of head(key) as appropriate.
 # by= always keeps data appearance order, so it's which columns are grouped and selected that drive how much of key is retained

man/setDF.Rd

@@ -4,13 +4,13 @@
 \description{
  In \code{data.table} parlance, all \code{set*} functions change their input \emph{by reference}. That is, no copy is made at all, other than temporary working memory, which is as large as one column.. The only other \code{data.table} operator that modifies input by reference is \code{\link{:=}}. Check out the \code{See Also} section below for other \code{set*} function \code{data.table} provides.
 
- A helper function to convert a \code{data.table} to \code{data.frame} by reference. It does not handle lists or lists of data.tables. 
+ A helper function to convert a \code{data.table} or \code{list} of equal length to \code{data.frame} by reference.
 }
 \usage{
 setDF(x)
 }
 \arguments{
- \item{x}{ A \code{data.table}. }
+ \item{x}{ A \code{data.table}, \code{data.frame} or \code{list} of equal length. }
 }
 
 \details{
@@ -27,6 +27,10 @@ setDF(x)
 X = data.table(x=1:5, y=6:10)
 ## convert 'X' to data.frame, without any copy.
 setDF(X)
+
+X = list(x=1:5, y=6:10)
+# X is converted to a data.frame without any copy.
+setDF(X)
 }
 \keyword{ data }