Allow atvalue indexing in categorical axes

Author: iamed2

src/indexing.jl

@@ -249,6 +249,12 @@ function axisindexes(::Type{Categorical}, ax::AbstractVector, idx)
     i == 0 && throw(ArgumentError("index $idx not found"))
     i
 end
+function axisindexes(::Type{Categorical}, ax::AbstractVector, idx::Value)
+    val = idx.val
+    i = findfirst(ax, val)
+    i == 0 && throw(ArgumentError("index $val not found"))
+    i
+end
 # Categorical axes may be indexed by a vector of their elements
 function axisindexes(::Type{Categorical}, ax::AbstractVector, idx::AbstractVector)
     res = findin(ax, idx)

test/categoricalvector.jl

@@ -13,8 +13,11 @@ A = AxisArray(data[idx,:], AxisArrays.CategoricalVector(v[idx]), [:a, :b])
 v = AxisArrays.CategoricalVector(collect([1; 8; 10:15]))
 @test AxisArrays.axistrait(axes(A)[1]) <: AxisArrays.Categorical
 A = AxisArray(reshape(1:16, 8, 2), v, [:a, :b])
+
 @test A[Axis{:row}(AxisArrays.CategoricalVector([15]))] == AxisArray(reshape(A.data[8, :], 1, 2), AxisArrays.CategoricalVector([15]), [:a, :b])
 @test A[Axis{:row}(AxisArrays.CategoricalVector([15])), 1] == AxisArray([A.data[8, 1]], AxisArrays.CategoricalVector([15]))
+@test A[atvalue(15), :] == AxisArray(A.data[8, :], [:a, :b])
+@test A[atvalue(15), 1] == 8
 @test AxisArrays.axistrait(axes(A)[1]) <: AxisArrays.Categorical
 
 # TODO: maybe make this work? Would require removing or modifying Base.getindex(A::AxisArray, idxs::Idx...)