Merge pull request #45 from JuliaAI/confusion-matrix-cornercase

Resolve corner case issue around misleading error message

Author: ablaom

src/confusion_matrices.jl

@@ -364,11 +364,8 @@ end
 
 # ## Some helpers
 
-function combined_levels(ŷ, y)
-    unsorted = Set(skipmissing(y))
-    union!(unsorted, skipmissing(ŷ))
-    sort(collect(unsorted))
-end
+combined_levels(ŷ, y) = vcat(levels(ŷ), levels(y)) |> unique |> sort
+
 
 """
     permutation(perm, rev, levels)

test/confusion_matrices.jl

@@ -168,4 +168,15 @@ end
     @test cm2[2,1] == cm[1,2]
 end
 
+@testset "corner case " begin
+    y1 = categorical([collect("npnp")..., missing])
+    y2 = categorical([collect("nppn")..., missing], compress=true)
+    # set invalid levels:
+    cm = ConfusionMatrix(levels=[1, 2])
+    @test_throws(
+       StatisticalMeasures.ConfusionMatrices. ERR_ORPHANED_OBSERVATIONS,
+       cm(y1, y2),
+    )
+end
+
 true