In Julia (julialang.org) if you are rather interested in finding the indices (indexes) of the elements in an array that fulfils a certain boolean condition then find is your friend, like so:
julia> probs = [0.1, 0.2, 0.3, 0.4, 0.5]
5-element Array{Float64,1}:
0.1
0.2
0.3
0.4
0.5
julia> find(x->x>0.2, probs)
3-element Array{Int64,1}:
3
4
5
Conditional array indexing is a really nice convenience when one wants to access array items that fullfills a certain boolean criteria. This is done in Julia in the following way:
julia> probs = [0.1, 0.2, 0.3, 0.4, 0.5]
5-element Array{Float64,1}:
0.1
0.2
0.3
0.4
0.5
julia> probs[probs.>0.2]
3-element Array{Float64,1}:
0.3
0.4
0.5
Observe the “.” in the .> operator which signifies elemetwise comparison.
If you omit the “.” you will get the following error:
probs[probs>0.2]
ERROR: no method isless(Float64,Array{Float64,1})
in > at operators.jl:19
Tags: julia
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