Gather list columns

Fixes tidyverse#175
imanns · May 16, 2016 · bae80df · bae80df
1 parent 3dbcbf7
commit bae80df
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Showing 3 changed files with 18 additions and 4 deletions.
diff --git a/NEWS.md b/NEWS.md
@@ -1,5 +1,7 @@
 # tidyr 0.4.1.9000
 
+* `gather()` can now gather together list columns (#175).
+
 * `unite()` and `separate()` now automatically drop removed variables from
   grouping (#159, #177).
 

diff --git a/src/melt.cpp b/src/melt.cpp
@@ -152,8 +152,14 @@ SEXP concatenate(const DataFrame& x, IntegerVector ind, bool factorsAsStrings) {
         }
         break;
       }
-      case RAWSXP:
-        DO_CONCATENATE(Rbyte);
+      case VECSXP: {
+        for (int j = 0; j < nrow; ++j) {
+          SET_VECTOR_ELT(output, i * nrow + j, VECTOR_ELT(tmp, j));
+        }
+        break;
+      }
+    default:
+      stop("Unsupported type (%s)", Rf_type2char(max_type));
     }
   }
 
@@ -183,8 +189,8 @@ List melt_dataframe(const DataFrame& data,
 
   // Don't melt if the value variables are non-atomic
   for (int i = 0; i < n_measure; ++i) {
-    if (!Rf_isVectorAtomic(data[measure_ind[i]])) {
-      stop("Can't melt data.frames with non-atomic 'measure' columns");
+    if (!Rf_isVector(data[measure_ind[i]])) {
+      stop("Can't gather non-vector column %i", measure_ind[i] + 1);
     }
   }
 

diff --git a/tests/testthat/test-gather.R b/tests/testthat/test-gather.R
@@ -130,3 +130,9 @@ test_that("can handle list-columns", {
 
   expect_identical(out$y, df$y)
 })
+
+test_that("can gather list-columns", {
+  df <- dplyr::data_frame(x = 1:2, y = list(1, 2), z = list(3, 4))
+  out <- gather(df, k, v, y:z)
+  expect_equal(out$v, list(1, 2, 3, 4))
+})