How do I transform a vector into a Matrix

General Usage
2

Does this answer your question?

julia> m1 = [1.0 2.0]
1×2 Matrix{Float64}:
 1.0  2.0

julia> vec(m1)
2-element Vector{Float64}:
 1.0
 2.0

julia> reshape(m1, 2)
2-element Vector{Float64}:
 1.0
 2.0

Re-reading the title it seems you want to go the other way.

julia> v1 = [1.0, 2.0]
2-element Vector{Float64}:
 1.0
 2.0

julia> reshape(v1, (1,2))
1×2 Matrix{Float64}:
 1.0  2.0

julia> reshape(v1, (2,1))
2×1 Matrix{Float64}:
 1.0
 2.0

Also, you can broadcast foo with adding a ..

julia> v2 = [1,2,3]
3-element Vector{Int64}:
 1
 2
 3

julia> foo.(v2)
3-element Vector{Float64}:
 1.0
 2.0
 3.0

julia> M2 = [1 2 3]
1×3 Matrix{Int64}:
 1  2  3

julia> foo.(M2)
1×3 Matrix{Float64}:
 1.0  2.0  3.0