Index to grouped data frame using Dicts

NEWS.md

@@ -38,11 +38,13 @@
 * add `rownumber` to `DataFrameRow` ([#2356](https://github.com/JuliaData/DataFrames.jl/pull/2356))
 * allow passing column name to specify the position where a new columns should be
   inserted in `insertcols!` ([#2365](https://github.com/JuliaData/DataFrames.jl/pull/2365))
+* allow `GroupedDataFrame`s to be indexed using a dictionary, which can use `Symbol` or string keys and 
+  are not dependent on the order of keys. ([#2281](https://github.com/JuliaData/DataFrames.jl/pull/2281))
 * add `isapprox` method to check for approximate equality between two dataframes
   ([#2373](https://github.com/JuliaData/DataFrames.jl/pull/2373))
 * add `columnindex` for `DataFrameRow`
   ([#2380](https://github.com/JuliaData/DataFrames.jl/pull/2380))
-
+  
 ## Deprecated
 
 * `DataFrame!` is now deprecated ([#2338](https://github.com/JuliaData/DataFrames.jl/pull/2338))

src/groupeddataframe/groupeddataframe.jl

@@ -245,15 +245,17 @@ Base.getindex(gd::GroupedDataFrame, idxs::Colon) =
 
 Key for one of the groups of a [`GroupedDataFrame`](@ref). Contains the values
 of the corresponding grouping columns and behaves similarly to a `NamedTuple`,
-but using it to index its `GroupedDataFrame` is much more effecient than using the
-equivalent `Tuple` or `NamedTuple`.
+but using it to index its `GroupedDataFrame` is more efficient than using the
+equivalent `Tuple` and `NamedTuple`, and much more efficient than using
+the equivalent `AbstractDict`.
 
 Instances of this type are returned by `keys(::GroupedDataFrame)` and are not
 meant to be constructed directly.
 
 Indexing fields of `GroupKey` is allowed using an integer, a `Symbol`, or a string.
 It is also possible to access the data in a `GroupKey` using the `getproperty`
-function. A `GroupKey` can be converted to a `Tuple`, `NamedTuple`, or `Vector`.
+function. A `GroupKey` can be converted to a `Tuple`, `NamedTuple`, a `Vector`, or 
+a `Dict`. When converted to a `Dict`, the keys of the `Dict` are `Symbol`s.
 
 See [`keys(::GroupedDataFrame)`](@ref) for more information.
 """
@@ -328,6 +330,8 @@ Base.convert(::Type{Array{T}}, key::GroupKey) where {T} = Vector{T}(key)
 Base.Array(key::GroupKey) = Vector(key)
 Base.Array{T}(key::GroupKey) where {T} = Vector{T}(key)
 
+Base.Dict(key::GroupKey) = Dict(pairs(key)...)
+
 Base.broadcastable(::GroupKey) =
     throw(ArgumentError("broadcasting over `GroupKey`s is reserved"))
 
@@ -367,7 +371,7 @@ function Base.getindex(gd::GroupedDataFrame, idx...)
 end
 
 # The allowed key types for dictionary-like indexing
-const GroupKeyTypes = Union{GroupKey, Tuple, NamedTuple}
+const GroupKeyTypes = Union{GroupKey, Tuple, NamedTuple, AbstractDict{Symbol}, AbstractDict{<:AbstractString}}
 # All allowed scalar index types
 const GroupIndexTypes = Union{Integer, GroupKeyTypes}
 
@@ -387,6 +391,25 @@ function Base.to_index(gd::GroupedDataFrame, key::NamedTuple{N}) where {N}
     return Base.to_index(gd, Tuple(key))
 end
 
+function _dict_to_tuple(key::AbstractDict{<:AbstractString}, gd::GroupedDataFrame)
+    if length(key) != length(gd.cols)
+        throw(KeyError(key))
+    end
+
+    return ntuple(i -> key[String(gd.cols[i])], length(gd.cols))
+end
+
+function _dict_to_tuple(key::AbstractDict{Symbol}, gd::GroupedDataFrame)
+    if length(key) != length(gd.cols)
+        throw(KeyError(key))
+    end    
+
+    return ntuple(i -> key[gd.cols[i]], length(gd.cols))
+end
+
+Base.to_index(gd::GroupedDataFrame, key::Union{AbstractDict{Symbol},AbstractDict{<:AbstractString}}) = 
+    Base.to_index(gd, _dict_to_tuple(key, gd))
+
 # Array of (possibly non-standard) indices
 function Base.to_index(gd::GroupedDataFrame, idxs::AbstractVector{T}) where {T}
     # A concrete eltype which is <: GroupKeyTypes, don't need to check
@@ -409,6 +432,10 @@ function Base.to_index(gd::GroupedDataFrame, idxs::AbstractVector{T}) where {T}
         Tuple
     elseif E1 <: NamedTuple
         NamedTuple
+    elseif E1 <: AbstractDict{Symbol}
+        AbstractDict{Symbol}
+    elseif E1 <: AbstractDict{<:AbstractString}
+        AbstractDict{<:AbstractString}
     else
         throw(ArgumentError("Invalid index: $idx1 of type $E1"))
     end
@@ -463,7 +490,7 @@ end
 Get the set of keys for each group of the `GroupedDataFrame` `gd` as a
 [`GroupKeys`](@ref) object. Each key is a [`GroupKey`](@ref), which behaves like
 a `NamedTuple` holding the values of the grouping columns for a given group.
-Unlike the equivalent `Tuple` and `NamedTuple`, these keys can be used to index
+Unlike the equivalent `Tuple`, `NamedTuple`, and `AbstractDict`, these keys can be used to index
 into `gd` efficiently. The ordering of the keys is identical to the ordering of
 the groups of `gd` under iteration and integer indexing.
 
@@ -572,6 +599,9 @@ function Base.haskey(gd::GroupedDataFrame, key::NamedTuple{N}) where {N}
     return haskey(gd, Tuple(key))
 end
 
+Base.haskey(gd::GroupedDataFrame, key::AbstractDict{<:Union{Symbol, <:AbstractString}}) = 
+    haskey(gd, _dict_to_tuple(key, gd))
+
 Base.haskey(gd::GroupedDataFrame, key::Union{Signed,Unsigned}) =
     1 <= key <= length(gd)
 
@@ -580,8 +610,9 @@ Base.haskey(gd::GroupedDataFrame, key::Union{Signed,Unsigned}) =
 
 Get a group based on the values of the grouping columns.
 
-`key` may be a `NamedTuple` or `Tuple` of grouping column values (in the same
-order as the `cols` argument to `groupby`).
+`key` may be a `GroupKey`, `NamedTuple` or `Tuple` of grouping column values (in the same
+order as the `cols` argument to `groupby`). It may also be an `AbstractDict`, in which case the 
+order of the arguments does not matter. 
 
 # Examples
 
@@ -625,7 +656,7 @@ julia> get(gd, (:baz,), nothing)
 julia> get(gd, (:qux,), nothing)
 ```
 """
-function Base.get(gd::GroupedDataFrame, key::Union{Tuple, NamedTuple}, default)
+function Base.get(gd::GroupedDataFrame, key::GroupKeyTypes, default)
     try
         return gd[key]
     catch KeyError

src/groupeddataframe/splitapplycombine.jl

@@ -36,8 +36,10 @@ and combines the result into a data frame).
 [`GroupKey`](@ref) objects returned by [`keys(::GroupedDataFrame)`](@ref),
 which can also be used to get the values of the grouping columns for each group.
 `Tuples` and `NamedTuple`s containing the values of the grouping columns (in the
-same order as the `cols` argument) are also accepted as indices, but this will
-be slower than using the equivalent `GroupKey`.
+same order as the `cols` argument) are also accepted as indices. Finally,
+an `AbstractDict` can be used to index into a grouped data frame where
+the keys are column names of the data frame. The order of the keys does
+not matter in this case. 
 
 # See also
 
@@ -89,6 +91,14 @@ julia> gd[(a=3,)]
 │ 1   │ 3     │ 2     │ 3     │
 │ 2   │ 3     │ 2     │ 7     │
 
+julia> gd[Dict("a" => 3)]
+2×3 SubDataFrame
+│ Row │ a     │ b     │ c     │
+│     │ Int64 │ Int64 │ Int64 │
+├─────┼───────┼───────┼───────┤
+│ 1   │ 3     │ 2     │ 3     │
+│ 2   │ 3     │ 2     │ 7     │
+
 julia> gd[(3,)]
 2×3 SubDataFrame
 │ Row │ a     │ b     │ c     │

test/grouping.jl

@@ -1371,29 +1371,53 @@ end
         @test gd[NamedTuple(key)] ≅ gd[i]
         # Plain tuple
         @test gd[Tuple(key)] ≅ gd[i]
+        # Dict with `Symbol` keys
+        @test gd[Dict(key)] ≅ gd[i]
+        # Dict with string keys
+        @test gd[Dict([String(k) => v for (k, v) in pairs(key)]...)] ≅ gd[i]
+        # Dict with AbstractString keys
+        @test gd[Dict([Test.GenericString(String(k)) => v for (k, v)  in pairs(key)]...)] ≅ gd[i]
+        # Out of order Dict
+        @test gd[Dict([k => v for (k, v) in Iterators.reverse(pairs(key))]...)] ≅ gd[i]
+        # AbstractDict 
+        @test gd[Test.GenericDict(Dict(key))] ≅ gd[i]
     end
 
     # Equivalent value of different type
     @test gd[(a=:A, b=1.0)] ≅ gd[1]
 
     @test get(gd, (a=:A, b=1), nothing) ≅ gd[1]
     @test get(gd, (a=:A, b=3), nothing) == nothing
-
+    @test get(gd, (:A, 1), nothing) ≅ gd[1]
+    @test get(gd, (:A, 3), nothing) == nothing
+    @test get(gd, first(keys(gd)), gd) ≅ gd[1]
+    @test get(gd, Dict("a" => :A, "b" => 1), nothing) ≅ gd[1]
+    @test get(gd, Dict(:a => :A, :b => 1), nothing) ≅ gd[1]
+    @test get(gd, Dict(:b => 1, :a => :A), nothing) ≅ gd[1]
+    @test get(gd, Dict(:a => :A, :b => 3), nothing) == nothing
+
     # Wrong values
     @test_throws KeyError gd[(a=:A, b=3)]
     @test_throws KeyError gd[(:A, 3)]
     @test_throws KeyError gd[(a=:A, b="1")]
+    @test_throws KeyError gd[Dict(:a => :A, :b => "1")]
     # Wrong length
     @test_throws KeyError gd[(a=:A,)]
     @test_throws KeyError gd[(:A,)]
     @test_throws KeyError gd[(a=:A, b=1, c=1)]
     @test_throws KeyError gd[(:A, 1, 1)]
+    @test_throws KeyError gd[Dict(:a => :A, :b => 1, :c => 2)]
     # Out of order
     @test_throws KeyError gd[(b=1, a=:A)]
     @test_throws KeyError gd[(1, :A)]
     # Empty
     @test_throws KeyError gd[()]
     @test_throws KeyError gd[NamedTuple()]
+    @test_throws KeyError gd[Dict{String, Any}()]
+
+    # Bad Dict types
+    @test_throws ArgumentError gd[Dict()]
+    @test_throws ArgumentError gd[Dict(1 => :A, 2 => 1)]
 end
 
 @testset "GroupKey and GroupKeys" begin
@@ -1524,7 +1548,7 @@ end
         gkeys = keys(gd)[ints]
 
         # Test with GroupKeys, Tuples, and NamedTuples
-        for converter in [identity, Tuple, NamedTuple]
+        for converter in [identity, Tuple, NamedTuple, Dict]
             a = converter.(gkeys)
             @test gd[a] ≅ gd2