问题
I would like to sort my matrix A by column 2 then 3.
A = round.(randn(100,4))
Maybe something like:
sort(A,(0,2:3))
100x4 Array{Float64,2}:
0.0 -2.0 -2.0 -1.0
-1.0 -2.0 -1.0 1.0
1.0 -2.0 -1.0 2.0
-1.0 -2.0 0.0 0.0
-1.0 -2.0 0.0 -1.0
-0.0 -2.0 0.0 -1.0
1.0 -2.0 0.0 0.0
1.0 -2.0 1.0 -1.0
-0.0 -2.0 2.0 -1.0
-0.0 -1.0 -2.0 1.0
⋮
-0.0 1.0 0.0 1.0
1.0 1.0 1.0 1.0
0.0 1.0 1.0 -1.0
-0.0 1.0 2.0 0.0
-0.0 2.0 -1.0 0.0
-2.0 2.0 -1.0 1.0
2.0 2.0 -0.0 -1.0
-1.0 2.0 -0.0 -1.0
1.0 2.0 0.0 2.0
-1.0 2.0 2.0 0.0
回答1:
There is a sortrows function that takes a by keyword that lets you do this:
julia> sortrows(A, by=x->(x[2],x[3]))
100x4 Array{Float64,2}:
2.0 -3.0 -0.0 0.0
-1.0 -2.0 -1.0 -1.0
-0.0 -2.0 -0.0 0.0
0.0 -2.0 0.0 -1.0
1.0 -2.0 1.0 2.0
-0.0 -2.0 1.0 -1.0
-1.0 -1.0 -2.0 1.0
-1.0 -1.0 -2.0 -0.0
-1.0 -1.0 -1.0 1.0
-0.0 -1.0 -1.0 0.0
⋮
-0.0 1.0 1.0 -1.0
-0.0 1.0 2.0 1.0
0.0 1.0 2.0 0.0
-1.0 2.0 -2.0 1.0
0.0 2.0 -2.0 -2.0
1.0 2.0 -1.0 0.0
0.0 2.0 -1.0 -0.0
-1.0 2.0 0.0 -1.0
-0.0 2.0 2.0 0.0
1.0 3.0 2.0 1.0
The sorting API is pretty flexible – you can find documentation here.
来源：https://stackoverflow.com/questions/23187752/julia-sort-matrix-by-column-2-then-3