Julia Language: How to create an array of structs inside a for loop

Question

here in this code, I am trying to create an array of struct called Linestruct

but I am getting this error "bound error, attempts to access0-element array..."

using CSV
df=CSV.read("F:/B/Mayar/lineData.CSV")

struct Linestruct
    buses::Vector{Int}
    res::Float64
    ind::Float64
    imp_mag::Float64
    imp_angle::Float64
    p::Float64
    q::Float64
    state::String
end
CREATE_Linestruct() = Linestruct([0,0], 0.0,
    0.0, 0.0, 0.0, 0.0, 0.0, "overloaded")
Linestruct(buses_line, res_line, ind_line) = Linestruct(buses_line, res_line,
    ind_line, 0.0, 0.0, 0.0, 0.0, "overloaded")

l2 = Linestruct([1,2,3], 0.0, 0.0)
l3=CREATE_Linestruct()
number_lines=size(df,1)
array_lines=Array{Linestruct,1}()

for x in 1:N
l4=CREATE_Linestruct()
array_lines[x]=l4


end

Answer 1

The issue is that the line

array_lines=Array{Linestruct,1}()

creates an empty array (i.e an array of size 0).

Afterwards, the line

array_lines[x]=l4

does not make the aray grow (unlike what would happen in a language like Matlab): it tries to change the value at index x in the array. Since the array is empty, you get an error.

A minimal example reproducing this situation might be (note that I'm using a vector of Int values here, since your problem is not really related to the array storing structs rather than native types):

julia> a = Array{Int, 1}()
0-element Array{Int64,1}

julia> a[1] = 1
ERROR: BoundsError: attempt to access 0-element Array{Int64,1} at index [1]

A way to fix this could be to make the array grow using push! to insert new values at the end of it:

julia> for i in 1:3
           push!(a, i)
       end

julia> a
3-element Array{Int64,1}:
 1
 2
 3