Julia: Arrays

Array is a collection of elements stored in multi dimensional grid, unlike other languages all the elements in array need not to be of same type.

julia> arr1=[2, "Hi", 23.5]
3-element Array{Any,1}:
  2    
   "Hi"
 23.5  

julia> typeof(arr1)
Array{Any,1}

‘,’ is not necessary while defining an array. You can define array using space(Instead of separating elements by ,) also.

julia> arr1=[1 2 3]
1x3 Array{Int64,2}:
 1  2  3

Get number of elements in array

length(A) function is used to get number of elements in array A.

julia> length(arr1)
3

Get type of elements contained in array

eltype(A) return the type of elements contained in array A.

julia> arr2=[1, 2, "Hi", 23.456]
4-element Array{Any,1}:
  1    
  2    
   "Hi"
 23.456

julia> eltype(arr2)
Any

julia> arr3=["Hi" "How" "are" "you"]
1x4 Array{ASCIIString,2}:
 "Hi"  "How"  "are"  "you"

julia> eltype(arr3)
ASCIIString

Accessing elements of array

You can access elements of array using index notation. A[1] is used to access first element of array A, A[2] is used to access 2^nd element of array A, A[end] is used to access the last element of array A.

julia> arr3
1x4 Array{ASCIIString,2}:
 "Hi"  "How"  "are"  "you"

julia> arr3[1]
"Hi"

julia> arr3[end]
"you"

julia> arr3[end-1]
"are"

Iterate over array

eachindex(A) returns an iterator to iterate over each position in the array.

julia> for i in eachindex(arr3)
           println(i," ", arr3[i])
       end
1 Hi
2 How
3 are
4 you

Pass by reference

In Julia, arrays are passed to functions by reference, so any changes made to the array inside the function are available outside the function also.

julia> function addXtoArray(arr, a)
           for i in eachindex(arr)
               arr[i] += a
           end
       end
addXtoArray (generic function with 1 method)

julia> arr1=[2, 3, 5, 7, 11]
5-element Array{Int64,1}:
  2
  3
  5
  7
 11

julia> addXtoArray(arr1, 5)

julia> arr1
5-element Array{Int64,1}:
  7
  8
 10
 12
 16

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