rowwiseDT support for key

R/rowwiseDT.R

@@ -2,11 +2,23 @@ rowwiseDT = function(...) {
   x = substitute(list(...))[-1L]
   if (is.null(nms <- names(x)))
     stopf("Must provide at least one column (use `name=`). See ?rowwiseDT for details")
+  if (length(key_pos <- which(nms == "key" & nzchar(x))) > 0L) {
+    if (length(key_pos) > 1L)
+      stopf("Key specified more than once")
+    if (length(key <- eval(x[[key_pos]], parent.frame())) == 1L)
+      key = cols_from_csv(key)
+    x = x[-key_pos]
+    nms = nms[-key_pos]
+  } else {
+    key_pos = 0L
+  }
   header_pos = which(nzchar(nms))
   if (any(nzchar(x[header_pos])))
     stopf("Named arguments must be empty")
   if (!identical(header_pos, seq_along(header_pos)))
     stopf("Header must be the first N arguments")
+  if (key_pos && !key_pos %in% c(1L, length(x) + 1L))
+    stopf("Key specification must be either the first or the last argument")
   header = nms[header_pos]
   ncols = length(header)
   body = lapply(x[-header_pos], eval, envir = parent.frame())
@@ -27,5 +39,7 @@ rowwiseDT = function(...) {
   body = split(body, rep(seq_len(nrows), each = ncols))
   ans = rbindlist(body)
   setnames(ans, header)
+  if (key_pos)
+    setkeyv(ans, key)
   ans
 }

inst/tests/tests.Rraw

@@ -18843,6 +18843,15 @@ test(2282.08, rowwiseDT(A=,B=,1,2,C=,4), error="Header must be the first N argum
 # evaluate arguments in the correct frame
 ncols = 1e6
 test(2282.09, rowwiseDT(A=,ncols), data.table(A=ncols))
+# tests involving key specification in rowwiseDT
+DT = data.table(A=1, B=2, key="B")
+test(2282.10, rowwiseDT(key="B", A=, B=, 1, 2), DT)
+test(2282.11, rowwiseDT(A=, B=, 1, 2, key="B"), DT)
+test(2282.12, rowwiseDT(A=, key=, B=, 1, 2, 3, key="B"), setDT(data.frame(A=1, key=2, B=3), key="B"))
+test(2282.13, rowwiseDT(A=, key="B", B=, 1, 2), error="Key specification must be either the first or the last argument")
+test(2282.14, rowwiseDT(key="A", key="B", A=, B=, key=, 1, 2, 3), error="Key specified more than once")
+# as "" equals to "missing", key = "" means column name (backwards compatible)
+test(2282.15, rowwiseDT(A="", B="", key="", 1, 2, 3), setDT(data.frame(A=1, B=2, key=3)))
 
 # test 2283 moved tests to optimize.Rraw
 

man/rowwiseDT.Rd

@@ -8,7 +8,7 @@
 rowwiseDT(...)
 }
 \arguments{
-  \item{...}{ Arguments that define the structure of a \code{data.table}. The column names come from named arguments (like \code{col=}), which must precede the data. See Examples. }
+  \item{...}{ Arguments that define the structure of a \code{data.table}. The column names come from named arguments (like \code{col=}), which must precede the data. A \code{key} can also be specified, given it is the first or last argument. See Examples. }
 }
 \value{
 A \code{data.table}. The default is for each column to return as a vector. However, if any entry has a length that is not one (e.g., \code{list(1, 2)}), the whole column will be converted to a list column.
@@ -20,6 +20,7 @@ A \code{data.table}. The default is for each column to return as a vector. Howev
 rowwiseDT(
   A=,B=, C=,
   1, "a",2:3,
-  2, "b",list(5)
+  2, "b",list(5),
+  key = "A"
 )
 }