Show group values when printing grouped dataframe (#1632)

src/groupeddataframe/show.jl

@@ -6,31 +6,51 @@ function Base.show(io::IO, gd::GroupedDataFrame;
                    rowlabel::Symbol = :Row,
                    summary::Bool = true)
     N = length(gd)
-    keys = join(':' .* string.(names(gd.parent)[gd.cols]), ", ")
+    keynames = names(gd.parent)[gd.cols]
+    parent_names = names(gd.parent)
+    keys = join(':' .* string.(keynames), ", ")
+
     keystr = length(gd.cols) > 1 ? "keys" : "key"
     groupstr = N > 1 ? "groups" : "group"
     summary && print(io, "$(typeof(gd)) with $N $groupstr based on $keystr: $keys")
     if allgroups
         for i = 1:N
             nrows = size(gd[i], 1)
             rows = nrows > 1 ? "rows" : "row"
-            print(io, "\nGroup $i: $nrows $rows")
+
+            identified_groups = [':' * string(parent_names[col], " = ", first(gd[i][col])) 
+                                 for col in gd.cols]
+
+            print(io, "\nGroup $i ($nrows $rows): ")
+            join(io, identified_groups, ", ")
+
             show(io, gd[i], summary=false,
                  allrows=allrows, allcols=allcols, rowlabel=rowlabel)
         end
     else
         if N > 0
             nrows = size(gd[1], 1)
             rows = nrows > 1 ? "rows" : "row"
-            print(io, "\nFirst Group: $nrows $rows")
+
+            identified_groups = [':' * string(parent_names[col], " = ", first(gd[1][col])) 
+                                 for col in gd.cols]
+
+            print(io, "\nFirst Group ($nrows $rows): ")
+            join(io, identified_groups, ", ")
+
             show(io, gd[1], summary=false,
                  allrows=allrows, allcols=allcols, rowlabel=rowlabel)
         end
         if N > 1
-            print(io, "\n⋮\n")
             nrows = size(gd[N], 1)
             rows = nrows > 1 ? "rows" : "row"
-            print(io, "Last Group: $nrows $rows")
+
+            identified_groups = [':' * string(parent_names[col], " = ", first(gd[N][col])) 
+                                 for col in gd.cols]
+            print(io, "\n⋮")
+            print(io, "\nLast Group ($nrows $rows): ")
+            join(io, identified_groups, ", ")
+
             show(io, gd[N], summary=false,
                  allrows=allrows, allcols=allcols, rowlabel=rowlabel)
         end

test/show.jl

@@ -235,13 +235,13 @@ module TestShow
     str = String(take!(io.io))
     @test str == """
     GroupedDataFrame{DataFrame} with 4 groups based on key: :A
-    First Group: 1 row
+    First Group (1 row): :A = 1
     │ Row │ A     │ B      │ C       │
     │     │ Int64 │ String │ Float32 │
     ├─────┼───────┼────────┼─────────┤
     │ 1   │ 1     │ x"     │ 1.0     │
     ⋮
-    Last Group: 1 row
+    Last Group (1 row): :A = 4
     │ Row │ A     │ B      │ C       │
     │     │ Int64 │ String │ Float32 │
     ├─────┼───────┼────────┼─────────┤
@@ -250,22 +250,22 @@ module TestShow
     str = String(take!(io.io))
     @test str == """
     GroupedDataFrame{DataFrame} with 4 groups based on key: :A
-    Group 1: 1 row
+    Group 1 (1 row): :A = 1
     │ Row │ A     │ B      │ C       │
     │     │ Int64 │ String │ Float32 │
     ├─────┼───────┼────────┼─────────┤
     │ 1   │ 1     │ x\"     │ 1.0     │
-    Group 2: 1 row
+    Group 2 (1 row): :A = 2
     │ Row │ A     │ B           │ C       │
     │     │ Int64 │ String      │ Float32 │
     ├─────┼───────┼─────────────┼─────────┤
     │ 1   │ 2     │ ∀ε>0: x+ε>x │ 2.0     │
-    Group 3: 1 row
+    Group 3 (1 row): :A = 3
     │ Row │ A     │ B      │ C       │
     │     │ Int64 │ String │ Float32 │
     ├─────┼───────┼────────┼─────────┤
     │ 1   │ 3     │ z\$     │ 3.0     │
-    Group 4: 1 row
+    Group 4 (1 row): :A = 4
     │ Row │ A     │ B      │ C       │
     │     │ Int64 │ String │ Float32 │
     ├─────┼───────┼────────┼─────────┤