From 2eb1f1182468d30777519689e2d3527d15ea7d78 Mon Sep 17 00:00:00 2001
From: Kevin Ushey <kevinushey@gmail.com>
Date: Wed, 6 Apr 2016 14:29:28 -0700
Subject: [PATCH] melt.data.frame drops 'dim' attribute for 'value' column
 (#77)

---
 NEWS.md                    | 3 +++
 R/utils.r                  | 8 ++++++--
 tests/testthat/test-melt.r | 9 +++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/NEWS.md b/NEWS.md
index 20db119..81b11ec 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # Version 1.4.1.9000
 
+* `melt.data.frame()` always drops the `dim` attribute on generated
+  value columns. (#77)
+
 * `melt.data.frame()` throws when encountering objects of type `POSIXlt`,
   and requests a conversion to the (much saner) `POSIXct` type.
 
diff --git a/R/utils.r b/R/utils.r
index e26ecf3..3d0761a 100644
--- a/R/utils.r
+++ b/R/utils.r
@@ -34,14 +34,18 @@ normalize_melt_arguments <- function(data, measure.ind, factorsAsStrings) {
 
   ## If we are going to be coercing any factors to strings, we don't want to
   ## copy the attributes
-  any.factors <- any( sapply( measure.ind, function(i) {
-    is.factor( data[[i]] )
+  any.factors <- any(sapply(measure.ind, function(i) {
+    is.factor(data[[i]])
   }))
 
   if (factorsAsStrings && any.factors) {
     measure.attributes <- NULL
   }
 
+  # Drop dimensions
+  if ("dim" %in% names(measure.attributes))
+    measure.attributes[["dim"]] <- NULL
+
   list(
     measure.attributes = measure.attributes,
     factorsAsStrings = factorsAsStrings
diff --git a/tests/testthat/test-melt.r b/tests/testthat/test-melt.r
index c0a2342..628b858 100644
--- a/tests/testthat/test-melt.r
+++ b/tests/testthat/test-melt.r
@@ -226,3 +226,12 @@ test_that("melt.data.frame throws when encountering POSIXlt", {
   expect_error(melt(df, measure.vars = c("x", "y")))
 
 })
+
+test_that("melt.data.frame drops dimensions on melted values", {
+
+  df <- data.frame(x = 1:5, y = letters[1:5], stringsAsFactors = FALSE)
+  attr(df$x, "dim") <- 5
+  melted <- melt(df, id = "y")
+  expect_true(is.null(attr(melted$value, "dim")))
+
+})