Fix compat + nested TermTuple (#4)

* compat for combinatorics

* support TupleTerm as innermost nesting

* slight consistency change

Project.toml

@@ -8,6 +8,7 @@ Combinatorics = "861a8166-3701-5b0c-9a16-15d98fcdc6aa"
 StatsModels = "3eaba693-59b7-5ba5-a881-562e759f1c8d"
 
 [compat]
+Combinatorics = "1"
 StatsBase = "0.33"
 StatsModels = "0.6.7"
 julia = "1.6"

src/nesting.jl

@@ -4,6 +4,13 @@ function _isfulldummy(x::CategoricalTerm)
     return isa(x.contrasts, StatsModels.ContrastsMatrix{StatsModels.FullDummyCoding})
 end
 
+function _fulldummycheck(outer::InteractionTerm)
+    all(_isfulldummy, outer.terms[1:end-1]) ||
+        throw(ArgumentError("Outer interactions in a nesting must consist only " *
+                            " of categorical terms with FullDummyCoding, got $outer"))
+    return nothing
+end
+
 """
     group / term
 
@@ -14,19 +21,29 @@ function Base.:(/)(outer::CategoricalTerm, inner::AbstractTerm)
     return outer + fulldummy(outer) & inner
 end
 
-function Base.:(/)(outer::TermTuple, inner::AbstractTerm)
+function Base.:(/)(outer::CategoricalTerm, inner::TermTuple)
+    fd = fulldummy(outer)
+    return mapfoldl(x -> fd & x, +, inner; init=outer)
+end
+
+function Base.:(/)(outer::TermTuple, inner::Union{AbstractTerm, TermTuple})
     return outer[1:end-1] + last(outer) / inner
 end
 
 function Base.:(/)(outer::InteractionTerm, inner::AbstractTerm)
     # we should only get here via expansion where the interaction term,
     # but who knows what devious things users will try
-    all(_isfulldummy, outer.terms[1:end-1]) ||
-        throw(ArgumentError("Outer interactions in a nesting must consist only " *
-                            " of categorical terms with FullDummyCoding, got $outer"))
+    _fulldummycheck(outer)
     return outer + outer & inner
 end
 
+function Base.:(/)(outer::InteractionTerm, inner::TermTuple)
+    # we should only get here via expansion where the interaction term,
+    # but who knows what devious things users will try
+    _fulldummycheck(outer)
+    return mapfoldl(x -> outer & x, +, inner; init=outer)
+end
+
 function Base.:(/)(outer::AbstractTerm, inner::AbstractTerm)
     throw(ArgumentError("nesting terms requires categorical grouping term, got $outer / $inner " *
                         "Manually specify $outer as `CategoricalTerm` in hints/contrasts"))

test/nesting.jl

@@ -31,6 +31,19 @@ end
     m = fit(DummyMod, @formula(y ~ 1 + a / x), dat)
     @test coefnames(m) == ["(Intercept)", "a: o", "a: u",
                            "a: i & x", "a: o & x", "a: u & x"]
+
+    m = fit(DummyMod, @formula(y ~ 0 + a / (b + x)), dat)
+    @test coefnames(m) == ["a: i", "a: o", "a: u",
+                           "a: i & b: q", "a: o & b: q", "a: u & b: q",
+                           "a: i & b: w", "a: o & b: w", "a: u & b: w",
+                           "a: i & x", "a: o & x", "a: u & x"]
+    m = fit(DummyMod, @formula(y ~ 0 + a / (b * x)), dat)
+    @test coefnames(m) == ["a: i", "a: o", "a: u",
+                           "a: i & b: q", "a: o & b: q", "a: u & b: q",
+                           "a: i & b: w", "a: o & b: w", "a: u & b: w",
+                           "a: i & x", "a: o & x", "a: u & x",
+                           "a: i & b: q & x", "a: o & b: q & x", "a: u & b: q & x",
+                           "a: i & b: w & x", "a: o & b: w & x", "a: u & b: w & x"]
 end
 
 @testset "multiple nesting levels" begin
@@ -68,4 +81,19 @@ end
                            "a: i & b: q & x", "a: o & b: q & x",
                            "a: u & b: q & x", "a: i & b: w & x",
                            "a: o & b: w & x", "a: u & b: w & x"]
+
+    m = fit(DummyMod, @formula(y ~ 0 + a / b / (c * x)), dat)
+    @test coefnames(m) == ["a: i", "a: o", "a: u",
+                           "a: i & b: q", "a: o & b: q", "a: u & b: q",
+                           "a: i & b: w", "a: o & b: w", "a: u & b: w",
+                           "a: i & b: q & c: f", "a: o & b: q & c: f", "a: u & b: q & c: f",
+                           "a: i & b: w & c: f", "a: o & b: w & c: f", "a: u & b: w & c: f",
+                           "a: i & b: q & c: s", "a: o & b: q & c: s", "a: u & b: q & c: s",
+                           "a: i & b: w & c: s", "a: o & b: w & c: s", "a: u & b: w & c: s",
+                           "a: i & b: q & x", "a: o & b: q & x", "a: u & b: q & x",
+                           "a: i & b: w & x", "a: o & b: w & x", "a: u & b: w & x",
+                           "a: i & b: q & c: f & x", "a: o & b: q & c: f & x", "a: u & b: q & c: f & x",
+                           "a: i & b: w & c: f & x", "a: o & b: w & c: f & x", "a: u & b: w & c: f & x",
+                           "a: i & b: q & c: s & x", "a: o & b: q & c: s & x", "a: u & b: q & c: s & x",
+                           "a: i & b: w & c: s & x", "a: o & b: w & c: s & x", "a: u & b: w & c: s & x"]
 end