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| # # STRUCT AND CONSTRUCTORS | ||
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| const WARN_DEGREE = "The `degree` must be at least 1. "* | ||
| "Reset `degree=2`. " | ||
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| mutable struct PolynomialTransformer <: Static | ||
| degree::Int | ||
| features::Union{Nothing, Vector{Symbol}} | ||
| interactions_only::Bool | ||
| end | ||
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| function MMI.clean!(model::PolynomialTransformer) | ||
| message = "" | ||
| if model.degree ≤ 0 | ||
| model.degree = 2 | ||
| message *= WARN_DEGREE | ||
| end | ||
| return message | ||
| end | ||
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| function PolynomialTransformer( | ||
| ; order=2, | ||
| degree=order, | ||
| features=nothing, | ||
| interactions_only=false, | ||
| ) | ||
| model = PolynomialTransformer(degree, features, interactions_only) | ||
| message = MMI.clean!(model) | ||
| isempty(message) || @warn message | ||
| return model | ||
| end | ||
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| # # HELPERS | ||
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| abstract type Selection end | ||
| struct WithRepetitions <: Selection end | ||
| struct WithoutRepetitions <: Selection end | ||
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| """ | ||
| premonomials(alphabet, degree, kind_of_selection::Selection) | ||
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| *Private method* to help generate monomials. A **pre-monomial** is a vector with elements | ||
| from the alphabet, with possible repetitions, but with no element predecessor coming | ||
| *after* the element itself in the alphabet. | ||
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| Note degree one "pre-monomials" are excluded. | ||
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| # Example | ||
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| ```julia-repl | ||
| julia> premonomials((:x, :y, :z), 3, WithoutRepetitions()) | ||
| 4-element Vector{Vector{Symbol}}: | ||
| [:x, :y] | ||
| [:x, :z] | ||
| [:y, :z] | ||
| [:x, :y, :z] | ||
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| julia> premonomials((:x, :y, :z), 3, WithRepetitions()) | ||
| 16-element Vector{Vector{Symbol}}: | ||
| [:x, :x] | ||
| [:x, :y] | ||
| [:x, :z] | ||
| [:y, :y] | ||
| [:y, :z] | ||
| [:z, :z] | ||
| [:x, :x, :x] | ||
| [:x, :x, :y] | ||
| [:x, :x, :z] | ||
| [:x, :y, :y] | ||
| [:x, :y, :z] | ||
| [:x, :z, :z] | ||
| [:y, :y, :y] | ||
| [:y, :y, :z] | ||
| [:y, :z, :z] | ||
| [:z, :z, :z] | ||
| ``` | ||
| """ | ||
| premonomials(alphabet, degree, ::WithoutRepetitions) = | ||
| premonomials(alphabet, degree, Combinatorics.combinations) | ||
| premonomials(alphabet, degree, ::WithRepetitions) = | ||
| premonomials(alphabet, degree, Combinatorics.with_replacement_combinations) | ||
| premonomials(alphabet, degree, fnctn) = | ||
| collect(Iterators.flatten(fnctn(alphabet, i) for i in 2:degree)) | ||
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| column_product(columns, premonomial...) = | ||
| .*((Tables.getcolumn(columns, feature) for feature in premonomial)...) | ||
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| # # CORE IMPLEMENTATION | ||
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| function MMI.transform(model::PolynomialTransformer, _, X) | ||
| features = MLJTransforms.actualfeatures(model.features, X) | ||
|
Contributor
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There was a problem hiding this comment. Not necessary but helpful for maintenance: The method |
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| kind_of_selection = model.interactions_only ? WithoutRepetitions() : WithRepetitions() | ||
| premonomials = MLJTransforms.premonomials(features, model.degree, kind_of_selection) | ||
| new_features = Tuple(Symbol(join(premon, "_")) for premon in premonomials) | ||
| materializer = Tables.materializer(X) | ||
| columns = Tables.Columns(X) | ||
| table_addendum = | ||
| NamedTuple{new_features}( | ||
| [column_product(columns, premon...) for premon in premonomials], | ||
| ) | ||
| return merge(Tables.columntable(X), table_addendum) |> materializer | ||
| end | ||
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| # # TRAITS | ||
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| metadata_model(PolynomialTransformer, | ||
| input_scitype = Tuple{Table}, | ||
| output_scitype = Table, | ||
| human_name = "polynomial transformer", | ||
| load_path = "MLJTransforms.PolynomialTransformer") | ||
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| # Package metadata for docstring generation | ||
| metadata_pkg(PolynomialTransformer, | ||
| package_name = "MLJTransforms", | ||
| package_uuid = "23777cdb-d90c-4eb0-a694-7c2b83d5c1d6", | ||
| package_url = "https://github.com/JuliaAI/MLJTransforms.jl", | ||
| is_pure_julia = true, | ||
| package_license = "MIT") | ||
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| """ | ||
| $(MLJModelInterface.doc_header(PolynomialTransformer)) | ||
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| This `Static` transformer generates new features comprised of monomials in existing | ||
| features that have `Continuous` or `Count` scitype, up to some specified degree. A | ||
| restricted set of features may be specified, and one may elect to generate only | ||
| interaction monomials (no feature appearing with degree higher than one). | ||
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| In MLJ or MLJBase, you can transform features `X` with the single call | ||
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| transform(machine(model), X) | ||
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| See also the example below. | ||
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| # Hyper-parameters | ||
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| - `degree=2`: maximum degree of monomials to be generated | ||
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| - `features=nothing`: vector of features for which monomials should be generated; if | ||
| `nothing` (unspecified) then all `Continuous` and `Count` features are used. | ||
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| # Operations | ||
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| - `transform(machine(model), X)`: Generate a new table from `X` with the monomial columnn | ||
| specified by hyper-parameters. | ||
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| # Example | ||
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| ``` | ||
| using MLJ | ||
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| X = ( | ||
| A = [1, 2, 3], | ||
| B = [4, 5, 6], | ||
| C = [7, 8, 9], | ||
| D = ["cat", "dog", "rat"] | ||
| ) | ||
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| transformer = PolynomialTransformer(degree=2, features=[:A, :B]) | ||
| mach = machine(transformer) | ||
| julia> transform(mach, X) |> pretty | ||
| ┌───────┬───────┬───────┬─────────┬───────┬───────┬───────┐ | ||
| │ A │ B │ C │ D │ A_A │ A_B │ B_B │ | ||
| │ Int64 │ Int64 │ Int64 │ String │ Int64 │ Int64 │ Int64 │ | ||
| │ Count │ Count │ Count │ Textual │ Count │ Count │ Count │ | ||
| ├───────┼───────┼───────┼─────────┼───────┼───────┼───────┤ | ||
| │ 1 │ 4 │ 7 │ cat │ 1 │ 4 │ 16 │ | ||
| │ 2 │ 5 │ 8 │ dog │ 4 │ 10 │ 25 │ | ||
| │ 3 │ 6 │ 9 │ rat │ 9 │ 18 │ 36 │ | ||
| └───────┴───────┴───────┴─────────┴───────┴───────┴───────┘ | ||
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| transformer = PolynomialTransformer(degree=3, interactions_only=true) | ||
| mach = machine(transformer) | ||
| julia> transform(mach, X) |> pretty | ||
| ┌───────┬───────┬───────┬─────────┬───────┬───────┬───────┬───────┐ | ||
| │ A │ B │ C │ D │ A_B │ A_C │ B_C │ A_B_C │ | ||
| │ Int64 │ Int64 │ Int64 │ String │ Int64 │ Int64 │ Int64 │ Int64 │ | ||
| │ Count │ Count │ Count │ Textual │ Count │ Count │ Count │ Count │ | ||
| ├───────┼───────┼───────┼─────────┼───────┼───────┼───────┼───────┤ | ||
| │ 1 │ 4 │ 7 │ cat │ 4 │ 7 │ 28 │ 28 │ | ||
| │ 2 │ 5 │ 8 │ dog │ 10 │ 16 │ 40 │ 80 │ | ||
| │ 3 │ 6 │ 9 │ rat │ 18 │ 27 │ 54 │ 162 │ | ||
| └───────┴───────┴───────┴─────────┴───────┴───────┴───────┴───────┘ | ||
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| ``` | ||
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| """ | ||
| PolynomialTransformer | ||
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why not throwing here?
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clean!mutates the model parameter so that it is valid, so no need to throw an exception. Or am I missing the point of your question?There was a problem hiding this comment.
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I suppose I am wondering whether it would be better to explicitly throw if a user's code does not make sense rather than assuming a fallback to
order=2?