Julia initiliase a vector of an array of vectors

When working with Julia, it is common to initialize vectors and arrays. In some cases, you may even need to initialize a vector of an array of vectors. In this article, we will explore three different ways to solve this problem.

Option 1: Using nested loops

One way to initialize a vector of an array of vectors is by using nested loops. Here is an example:

# Initialize the vector
vector_of_arrays = Vector{Array{Vector{Int}, 1}}()

# Initialize the arrays
for i in 1:5
    array_of_vectors = Array{Vector{Int}, 1}()
    
    # Initialize the vectors
    for j in 1:3
        vector = Vector{Int}()
        push!(vector, j)
        push!(array_of_vectors, vector)
    end
    
    push!(vector_of_arrays, array_of_vectors)
end

This code snippet initializes a vector called vector_of_arrays and then uses nested loops to initialize the arrays and vectors within it. The outer loop iterates 5 times to create 5 arrays, and the inner loop iterates 3 times to create 3 vectors within each array. Finally, the arrays and vectors are pushed into the vector_of_arrays vector.

Option 2: Using comprehensions

Another way to initialize a vector of an array of vectors is by using comprehensions. Here is an example:

# Initialize the vector using comprehensions
vector_of_arrays = [ [ [j for j in 1:3] for i in 1:5 ] ]

This code snippet uses nested comprehensions to initialize the vector of arrays. The outer comprehension iterates 5 times to create 5 arrays, and the inner comprehension iterates 3 times to create 3 vectors within each array. The resulting vector of arrays is assigned to the vector_of_arrays variable.

Option 3: Using the fill function

The third option to initialize a vector of an array of vectors is by using the fill function. Here is an example:

# Initialize the vector using the fill function
vector_of_arrays = fill(fill(fill(0, 3), 3), 5)

This code snippet uses the fill function to initialize the vector of arrays. The innermost fill function creates a vector of zeros with a length of 3, the second fill function creates an array of vectors by filling it with the vector of zeros, and the outermost fill function creates the vector of arrays by filling it with the array of vectors. The resulting vector of arrays is assigned to the vector_of_arrays variable.

After exploring these three options, it is clear that using comprehensions is the most concise and readable way to initialize a vector of an array of vectors in Julia. It eliminates the need for nested loops and multiple function calls, resulting in cleaner and more efficient code.