Add stub for categorical (#13)

Author: tlienart

Project.toml

@@ -1,7 +1,7 @@
 name = "MLJModelInterface"
 uuid = "e80e1ace-859a-464e-9ed9-23947d8ae3ea"
 authors = ["Thibaut Lienart and Anthony Blaom"]
-version = "0.1.4"
+version = "0.1.5"
 
 [deps]
 ScientificTypes = "321657f4-b219-11e9-178b-2701a2544e81"

src/data_utils.jl

@@ -6,6 +6,15 @@ const REQUIRE = "(requires MLJBase to be loaded)"
 errlight(s) = throw(InterfaceError("Only `MLJModelInterface` is loaded. " *
                                     "Import `MLJBase` in order to use `$s`."))
 
+# ------------------------------------------------------------------------
+# categorical, note: not exported to avoid clashes; this is fine because
+# MLJBase loads CategoricalArrays and MLJ interfaces should use qualified
+# statements.
+
+categorical(a...; kw...) = categorical(get_interface_mode(), a...; kw...)
+
+categorical(::LightInterface, a...; kw...) = errlight("categorical")
+
 # ------------------------------------------------------------------------
 # matrix
 

test/data_utils.jl

@@ -1,3 +1,15 @@
+@testset "categorical-light" begin
+    setlight()
+    x = 1:5
+    @test_throws M.InterfaceError M.categorical(x)
+end
+@testset "categorical-full" begin
+    setfull()
+    M.categorical(::FI, a...; kw...) = categorical(a...; kw...)
+    x = 1:5
+    @test M.categorical(x) == categorical(x)
+end
+# ------------------------------------------------------------------------
 @testset "matrix-light" begin
     setlight()
     X = ones(2,3)