alvas alvas - 4 years ago 176
Python Question

How to combine countmap and proportionmap in Julia?

The countmap can collate the counts of items in a list:

import StatsBase: countmap, proportionmap, addcounts!
a = [1,2,3,4,1,2,2,3,1,2,5,7,4,8,4]
b = [1,2,5,3,1,6,1,6,1,2,6,2]
x, y = countmap(a), countmap(b)


[out]:

(Dict(7=>1,4=>3,2=>4,3=>2,5=>1,8=>1,1=>3),Dict(2=>3,3=>1,5=>1,6=>3,1=>4))


I could add the counts from the raw list into the
countmap
dictionary as such:

z = addcounts!(x, b)


[out]:

Dict{Int64,Int64} with 8 entries:
7 => 1
4 => 3
2 => 7
3 => 3
5 => 2
8 => 1
6 => 3
1 => 7


But if somehow I have already got a counted dictionary, I couldn't just add them:

addcounts!(x, y)


[error]:

MethodError: no method matching addcounts!(::Dict{Int64,Int64}, ::Dict{Int64,Int64})
Closest candidates are:
addcounts!{T}(::Dict{T,V}, ::AbstractArray{T,N}) at /Users/liling.tan/.julia/v0.5/StatsBase/src/counts.jl:230
addcounts!{T,W}(::Dict{T,V}, ::AbstractArray{T,N}, ::StatsBase.WeightVec{W,Vec<:AbstractArray{T<:Real,1}}) at /Users/liling.tan/.julia/v0.5/StatsBase/src/counts.jl:237


Neither did this work too:

x + y


[error]:

MethodError: no method matching +(::Dict{Int64,Int64}, ::Dict{Int64,Int64})
Closest candidates are:
+(::Any, ::Any, ::Any, ::Any...) at operators.jl:138


Is there a way to combine multiple
countmap
s ?


E.g. in Python:

>>> from collections import Counter
>>> a = [1,2,3,4,1,2,2,3,1,2,5,7,4,8,4]
>>> b = [1,2,5,3,1,6,1,6,1,2,6,2]
>>> x, y = Counter(a), Counter(b)
>>> z = x + y
>>> z
Counter({1: 7, 2: 7, 3: 3, 4: 3, 6: 3, 5: 2, 7: 1, 8: 1})

Answer Source

As Jun Zhang suggested DataStructures.jl provides Accumulator type (a.k.a counter). Specifically, to get the results in the question:

using DataStructures

x,y = counter(a),counter(b)

push!(x,y)          # push! replaces addcounts!

Now x containts the sum of x and y.

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