add Remainder, still need the tests

src/transforms/remainder.jl

@@ -10,18 +10,75 @@ and returns a new table with an additional column containing the
 remainder value `xₙ₊₁ = total .- (x₁ + x₂ + ⋯ + xₙ)` If the `total`
 value is not specified, then default to the maximum sum across rows.
 """
-struct Remainder <: Transform end
+struct Remainder <: Transform
+  total::Union{Float64,Nothing}
+end
+
+Remainder(total=nothing) = Remainder(total)
 
 isrevertible(::Type{Remainder}) = true
 
-function apply(::Remainder, table)
-  # TODO
+assertions(::Type{Remainder}) = [TT.assert_continuous]
+
+function apply(transform::Remainder, table)
+  # basic checks
+  for assertion in assertions(transform)
+    assertion(table)
+  end
+
+  # design matrix
+  X = Tables.matrix(table)
+
+  # find total across rows
+  total = if !isnothing(transform.total)
+    transform.total
+  else
+    maximum(sum(X, dims=2))
+  end
+
+  # original column names
+  names = Tables.columnnames(table)
+
+  # create a column with the remainder of each row
+  T = total .- S
+  Z = hcat(X, T)
+
+  # table with the new column
+  names = (names..., :remainder)
+  𝒯 = (; zip(names, eachcol(Z))...)
+
+  newtable = 𝒯 |> Tables.materializer(table)
+  newtable, total
 end
 
 function revert(::Remainder, newtable, cache)
-  # TODO
+  Reject(:remainder)(newtable)
 end
 
-function reapply(::Remainder, table, cache)
-  # TODO
+function reapply(transform::Remainder, table, cache)
+  # basic checks
+  for assertion in assertions(transform)
+    assertion(table)
+  end
+
+  # retrieve total from cache
+  total = cache
+
+  # original column names
+  names = Tables.columnnames(table)
+
+  # table as matrix and get the sum acros dims 2
+  X = Tables.matrix(table)
+  S = sum(X, dims=2)
+
+  # create a column with the remainder of each row
+  T = total .- S
+  Z = hcat(X, T)
+
+  # table with the new column
+  names = (names..., :remainder)
+  𝒯 = (; zip(names, eachcol(Z))...)
+
+  newtable = 𝒯 |> Tables.materializer(table)
+  newtable, total
 end

test/transforms.jl

@@ -29,4 +29,17 @@
   tilr = revert(ILR(:b), n, c)
   @test n    |> Tables.columnnames == (:a, :c)
   @test tilr |> Tables.columnnames == (:a, :b, :c)
+
+  # Tests for Remainder
+  t = (a=rand(100), b=rand(100), c=rand(100))
+  n, c = apply(Remainder(), t)
+  trem = revert(Remainder(), n, c)
+  @test Tables.matrix(n)[:, 1:end-1] == Tables.matrix(t)
+  @test all(x -> 0 ≤ x ≤ c, Tables.matrix(n)[:, end])
+  @test n    |> Tables.columnnames == (:a, :b, :c, :remainder)
+  @test trem |> Tables.columnnames == (:a, :b, :c)
+
+  t = (a=rand(100), b=rand(100), c=rand(100))
+  n, c = reapply(Remainder(), t, c)
+  @test all(x -> 0 ≤ x ≤ c, Tables.matrix(n)[:, end])
 end