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Merged
merged 2 commits into from
Aug 6, 2025
Merged

Return target columns in Map #302

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3fa5d1d
Return target columns in Map
juliohm Aug 6, 2025
be406eb
Remove unnecessary collect
juliohm Aug 6, 2025
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65 changes: 23 additions & 42 deletions src/transforms/map.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,11 @@
# Licensed under the MIT License. See LICENSE in the project root.
# ------------------------------------------------------------------

const TargetName = Union{Symbol,AbstractString}
const PairWithTarget = Pair{<:Any,<:Pair{<:Function,<:TargetName}}
const PairWithoutTarget = Pair{<:Any,<:Function}
const MapPair = Union{PairWithTarget,PairWithoutTarget}

"""
Map(cols₁ => fun₁ => target₁, cols₂ => fun₂, ..., colsₙ => funₙ => targetₙ)

Expand All @@ -13,8 +18,6 @@ a collection of identifiers or a regular expression (regex).

Passing a target column name is optional and when omitted a new name
is generated by joining the function name with the selected column names.
If the target column already exists in the table, the original
column will be replaced.

## Examples

Expand Down Expand Up @@ -44,16 +47,6 @@ end

Map() = throw(ArgumentError("cannot create Map transform without arguments"))

# utility types
const TargetName = Union{Symbol,AbstractString}
const PairWithTarget = Pair{<:Any,<:Pair{<:Function,<:TargetName}}
const PairWithoutTarget = Pair{<:Any,<:Function}
const MapPair = Union{PairWithTarget,PairWithoutTarget}

# utility functions
_extract(p::PairWithTarget) = selector(first(p)), first(last(p)), Symbol(last(last(p)))
_extract(p::PairWithoutTarget) = selector(first(p)), last(p), nothing

function Map(pairs::MapPair...)
tuples = map(_extract, pairs)
selectors = [t[1] for t in tuples]
Expand All @@ -62,32 +55,14 @@ function Map(pairs::MapPair...)
Map(selectors, funs, targets)
end

_funname(fun::Base.Fix1) = "fix1_" * _funname(fun.f)
_funname(fun::Base.Fix2) = "fix2_" * _funname(fun.f)
_funname(fun::ComposedFunction) = _funname(fun.outer) * "_" * _funname(fun.inner)
_funname(fun) = string(fun)

function _makename(snames, fun)
funname = _funname(fun)
if contains(funname, "#") # anonymous functions
funname = replace(funname, "#" => "f")
end
Symbol(funname, :_, join(snames, "_"))
end

function applyfeat(transform::Map, feat, prep)
cols = Tables.columns(feat)
onames = Tables.columnnames(cols)
names = Tables.columnnames(cols)

selectors = transform.selectors
funs = transform.funs
targets = transform.targets

# new names and columns
names = collect(onames)
columns = Any[Tables.getcolumn(cols, nm) for nm in onames]

# mapped columns
mapped = map(selectors, funs, targets) do selector, fun, target
snames = selector(names)
newname = isnothing(target) ? _makename(snames, fun) : target
Expand All @@ -96,17 +71,23 @@ function applyfeat(transform::Map, feat, prep)
newname => newcolumn
end

for (name, column) in mapped
if name ∈ onames
i = findfirst(==(name), onames)
columns[i] = column
else
push!(names, name)
push!(columns, column)
end
end
newfeat = (; mapped...) |> Tables.materializer(feat)

𝒯 = (; zip(names, columns)...)
newfeat = 𝒯 |> Tables.materializer(feat)
newfeat, nothing
end

_extract(p::PairWithTarget) = selector(first(p)), first(last(p)), Symbol(last(last(p)))
_extract(p::PairWithoutTarget) = selector(first(p)), last(p), nothing

_funname(fun::Base.Fix1) = "fix1_" * _funname(fun.f)
_funname(fun::Base.Fix2) = "fix2_" * _funname(fun.f)
_funname(fun::ComposedFunction) = _funname(fun.outer) * "_" * _funname(fun.inner)
_funname(fun) = string(fun)

function _makename(snames, fun)
funname = _funname(fun)
if contains(funname, "#") # anonymous functions
funname = replace(funname, "#" => "f")
end
Symbol(funname, :_, join(snames, "_"))
end
30 changes: 15 additions & 15 deletions test/transforms/map.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -9,55 +9,55 @@

T = Map(1 => sin)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :sin_a)
@test Tables.schema(n).names == (:sin_a,)
@test n.sin_a == sin.(t.a)

T = Map(:b => cos)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :cos_b)
@test Tables.schema(n).names == (:cos_b,)
@test n.cos_b == cos.(t.b)

T = Map("c" => tan)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :tan_c)
@test Tables.schema(n).names == (:tan_c,)
@test n.tan_c == tan.(t.c)

T = Map(:a => sin => :a)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d)
@test Tables.schema(n).names == (:a,)
@test n.a == sin.(t.a)

T = Map(:a => sin => "a")
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d)
@test Tables.schema(n).names == (:a,)
@test n.a == sin.(t.a)

T = Map([2, 3] => ((b, c) -> 2b + c) => :op1)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :op1)
@test Tables.schema(n).names == (:op1,)
@test n.op1 == @. 2 * t.b + t.c

T = Map([:a, :c] => ((a, c) -> 2a * 3c) => :op1)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :op1)
@test Tables.schema(n).names == (:op1,)
@test n.op1 == @. 2 * t.a * 3 * t.c

T = Map(["c", "a"] => ((c, a) -> 3c / a) => :op1, "c" => tan)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :op1, :tan_c)
@test Tables.schema(n).names == (:op1, :tan_c)
@test n.op1 == @. 3 * t.c / t.a
@test n.tan_c == tan.(t.c)

T = Map(r"[abc]" => ((a, b, c) -> a^2 - 2b + c) => "op1")
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :op1)
@test Tables.schema(n).names == (:op1,)
@test n.op1 == @. t.a^2 - 2 * t.b + t.c

# generated names
# normal function
T = Map([:c, :d] => hypot)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :hypot_c_d)
@test Tables.schema(n).names == (:hypot_c_d,)
@test n.hypot_c_d == hypot.(t.c, t.d)

# anonymous function
Expand All @@ -66,34 +66,34 @@
colname = Symbol(fname, :_a)
T = Map(:a => f)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, colname)
@test Tables.schema(n).names == (colname,)
@test Tables.getcolumn(n, colname) == f.(t.a)

# composed function
f = sin ∘ cos
T = Map(:b => f)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :sin_cos_b)
@test Tables.schema(n).names == (:sin_cos_b,)
@test n.sin_cos_b == f.(t.b)

f = sin ∘ cos ∘ tan
T = Map(:c => sin ∘ cos ∘ tan)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :sin_cos_tan_c)
@test Tables.schema(n).names == (:sin_cos_tan_c,)
@test n.sin_cos_tan_c == f.(t.c)

# Base.Fix1
f = Base.Fix1(hypot, 2)
T = Map(:d => f)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :fix1_hypot_d)
@test Tables.schema(n).names == (:fix1_hypot_d,)
@test n.fix1_hypot_d == f.(t.d)

# Base.Fix2
f = Base.Fix2(hypot, 2)
T = Map(:a => f)
n, c = apply(T, t)
@test Tables.schema(n).names == (:a, :b, :c, :d, :fix2_hypot_a)
@test Tables.schema(n).names == (:fix2_hypot_a,)
@test n.fix2_hypot_a == f.(t.a)

# error: cannot create Map transform without arguments
Expand Down
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