sorted indexes in Julia (equivalent to numpy's argsort)

Question

Which Julia's function returns the indexes that would sort an array? Python's Numpy uses argsort.

Answer 1

julia> r = rand(0:9, 5)
5-element Array{Int64,1}:
 5
 0
 6
 1
 1

julia> i = sortperm(r)
5-element Array{Int64,1}:
 2
 4
 5
 1
 3

julia> r[i]
5-element Array{Int64,1}:
 0
 1
 1
 5
 6

Answer 2

Im not 100% I understand the question, but I suspect that what you are asking, is that if you have the vector

a = [4,8,2]

you would like to get

order = [2,3,1]

If that's what you need, what I do is I use sortcols, which is a veird workaround

If you have a vector,

a = [5,2,8,4,3,1]

you create a new

b = hcat(a, 1:length(a))

 5  1
 2  2
 8  3
 4  4
 3  5
 1  6

then you call

c = sortrows(b, by = x -> x[1])

 1  6
 2  2
 3  5
 4  4
 5  1
 8  3

and now c[:,2] will be the latter column

 6
 2
 5
 4
 1
 3

Ofcourse, this can all be compressed into

sortrows(hcat(a, 1:length(a)), by = x -> x[1])[:,2]

but I felt like explaining how it works

Im really hoping someone posts a better way to do this, if one exists