If I have two arrays:
a = [ 1, 4, 3, 2]
b = ['z', 'w', 'x', 'y']
and I want to sort both a and b based on the values from a, i.e.:
[ 1, 2, 3, 4] # a
['z','y','x','w'] # b
What is an efficient/idiomatic way to do this?
With two distinct vectors I do not know if this is possible.
I would use sortperm that returns a permutation vector p that puts a[p] in sorted order
julia> p=sortperm(a)
4-element Vector{Int64}:
1
4
3
2
julia> a[p]
4-element Vector{Int64}:
1
2
3
4
julia> b[p]
4-element Vector{Char}:
'z': ASCII/Unicode U+007A (category Ll: Letter, lowercase)
'y': ASCII/Unicode U+0079 (category Ll: Letter, lowercase)
'x': ASCII/Unicode U+0078 (category Ll: Letter, lowercase)
'w': ASCII/Unicode U+0077 (category Ll: Letter, lowercase)
If performance is important you can also use sortperm! that allows using a preallocated permutation vector p.
Note: if you have a matrix you can use sortslices
julia> M=hcat(a,b)
4×2 Matrix{Any}:
1 'z'
4 'w'
3 'x'
2 'y'
julia> sortslices(M,dims=1,by=x->x[1])
4×2 Matrix{Any}:
1 'z'
2 'y'
3 'x'
4 'w'