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Julia appears to have a lot of Matlab like features. I'd like to select from an array using a predicate. In Matlab I can do this like:
>> a = 2:7 ; >> a > 4 ans = 0 0 0 1 1 1 >> a(a>4) ans = 5 6 7 I found a kind of clunky seeming way to do part of this in Julia:
julia> a = 2:7 2:7 julia> [int(x > 3) for x in a] 6-element Array{Any,1}: 0 0 1 1 1 1 (Using what wikipedia calls list comprehension). I haven't figured out how to apply a set like this to select with in Julia, but may be barking up the wrong tree. How would one do a predicate selection from an array in Julia?
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In Julia, to access the contents/particular element of an array, you need to write the name of the array with the element number in square bracket. Now let us access the elements of 2-D.
A Vector in Julia can be created with the use of a pre-defined keyword Vector() or by simply writing Vector elements within square brackets([]). There are different ways of creating Vector. vector_name = [value1, value2, value3,..] or vector_name = Vector{Datatype}([value1, value2, value3,..])
This is usually called with the syntax Type[] . Element values can be specified using Type[a,b,c,...] . zeros([T=Float64,] dims::Tuple) zeros([T=Float64,] dims...) Create an Array , with element type T , of all zeros with size specified by dims .
You can use a very Matlab-like syntax if you use a dot . for elementwise comparison:
julia> a = 2:7 2:7 julia> a .> 4 6-element BitArray{1}: false false false true true true julia> a[a .> 4] 3-element Array{Int32,1}: 5 6 7 Alternatively, you can call filter if you want a more functional predicate approach:
julia> filter(x -> x > 4, a) 3-element Array{Int32,1}: 5 6 7 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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