I am trying create a Dictionary from Arrays of Keys and Values
julia> id = [1,2,3,4];
julia> coord = [0 0 0;1 0 0;5 3 0;6 5 1];
and I want something like:
Dict(id,coord)
i.e.
julia> X = Dict(1 => [0,0,0],
2 => [1,0,0],
3 => [5,3,0],
4 => [6,5,1])
Dict{Int64,Array{Int64,1}} with 4 entries:
4 => [6, 5, 1]
2 => [1, 0, 0]
3 => [5, 3, 0]
1 => [0, 0, 0]
2 Likes
One way is Dict(zip(keys, values))
.
3 Likes
Or the slick new syntax Dict(ks .=> vs)
which simply falls out of broadcasting and the Dict
constructor.
29 Likes
It would be cool if the documentation had a “cool tricks that are hard to look up in the documentation” documentation page.
15 Likes
Thank you so much for your help.
I don’t get an array in the values (julia v0.7)
julia> Dict(id .=> coord)
Dict{Int64,Int64} with 4 entries:
4 => 1
2 => 0
3 => 0
1 => 0
i.e.
Dict{Int64,Array{Int64,1}} with 4 entries:
4 => [6, 5, 1]
2 => [1, 0, 0]
3 => [5, 3, 0]
1 => [0, 0, 0]
You need:
julia> Dict( id .=> [coord[i,:] for i=1:4] )
Dict{Int64,Array{Int64,1}} with 4 entries:
4 => [6, 5, 1]
2 => [1, 0, 0]
3 => [5, 3, 0]
1 => [0, 0, 0]
Also, this is faster:
julia> Dict( (id[i] => coord[i,:] for i=1:4) )
Dict{Int64,Array{Int64,1}} with 4 entries:
4 => [6, 5, 1]
2 => [1, 0, 0]
3 => [5, 3, 0]
1 => [0, 0, 0]
Edit: I left two extra unnecessary parens, thanks to @StefanKarpinski, this can be much nicer:
Dict( id[i] => coord[i,:] for i=1:4 )
4 Likes
You can drop one pair of parens in the latter one.
1 Like
Yes, this makes it much nicer, thank you.