Support CategoricalArrays 1 (#324)

Since `levels(::CategoricalArray)` now returns a `CategoricalArray`, we need to
unwrap the result before storing it as an `Array` field. This also works
on CategoricalArrays 0.10.

Author: nalimilan

src/contrasts.jl

@@ -157,7 +157,9 @@ ContrastsMatrix(contrasts_matrix::ContrastsMatrix, levels::AbstractVector)
   constructing a model matrix from a `ModelFrame` using different data.
 
 """
-function ContrastsMatrix(contrasts::C, levels::AbstractVector{T}) where {C<:AbstractContrasts, T}
+function ContrastsMatrix(contrasts::C, levels::AbstractVector) where {C<:AbstractContrasts}
+
+    u_levels = DataAPI.unwrap.(levels)
 
     # if levels are defined on contrasts, use those, validating that they line up.
     # what does that mean? either:
@@ -167,9 +169,9 @@ function ContrastsMatrix(contrasts::C, levels::AbstractVector{T}) where {C<:Abst
     #    better to filter data frame first
     # 3. contrast levels missing from data: would have empty columns, generate a
     #    rank-deficient model matrix.
-    c_levels = something(DataAPI.levels(contrasts), levels)
+    c_levels = something(DataAPI.levels(contrasts), u_levels)
 
-    mismatched_levels = symdiff(c_levels, levels)
+    mismatched_levels = symdiff(c_levels, u_levels)
     if !isempty(mismatched_levels)
         throw(ArgumentError("contrasts levels not found in data or vice-versa: " *
                             "$mismatched_levels." *
@@ -179,7 +181,7 @@ function ContrastsMatrix(contrasts::C, levels::AbstractVector{T}) where {C<:Abst
 
     # do conversion AFTER checking for levels so users get a nice error message
     # when they've made a mistake with the level types
-    c_levels = convert(Vector{T}, c_levels)
+    c_levels = convert(Vector{eltype(u_levels)}, c_levels)
 
     n = length(c_levels)
     if n == 0
@@ -228,7 +230,7 @@ end
 
 function StatsAPI.coefnames(C::AbstractContrasts, levels::AbstractVector, baseind::Integer)
     not_base = [1:(baseind-1); (baseind+1):length(levels)]
-    levels[not_base]
+    DataAPI.unwrap.(levels[not_base])
 end
 
 Base.getindex(contrasts::ContrastsMatrix, rowinds, colinds) =
@@ -594,7 +596,7 @@ function contrasts_matrix(C::HypothesisCoding, baseind, n)
 end
 
 StatsAPI.coefnames(C::HypothesisCoding, levels::AbstractVector, baseind::Int) =
-    something(C.labels, levels[1:length(levels) .!= baseind])
+    something(C.labels, DataAPI.unwrap.(levels[1:length(levels) .!= baseind]))
 
 DataAPI.levels(c::HypothesisCoding) = c.levels