So, I'm writing a function. In order to begin the computation, I need to create a vector of 1s. This is going to be multiplied by an inputted matrix A.
So if a matrix is 6x6, it becomes a vector of length 6, made up of 1s. If it's 4x4, it becomes a vector of length 4 with all values at 1.
How do I make the vector the right size for any given matrix A?
Suppose you have the following matrix A:
julia> A=reshape(1:9,3,3)
3×3 reshape(::UnitRange{Int64}, 3, 3) with eltype Int64:
1 4 7
2 5 8
3 6 9
Than you can do:
julia> A*ones(size(A,1))
3-element Vector{Float64}:
12.0
15.0
18.0
(If you rather meant a horizontal vector of ones you could do ones(1,size(A,1))*A)
Note that the same effect can be simply achieved with the dims parameter of the sum function:
julia> sum(A,dims=2)
3×1 Matrix{Int64}:
12
15
18
or if you want a Vector:
julia> vec(sum(A,dims=2))
3-element Vector{Int64}:
12
15
18