Provide vectors instead of matrix:
julia> [1.0 2.0]
1×2 Matrix{Float64}:
1.0 2.0
julia> [1.0, 2.0]
2-element Vector{Float64}:
1.0
2.0
julia> plot([1.0, 2.0],[2.0, 3.0], linewidth=2,legend=:false)

Provide vectors instead of matrix:
julia> [1.0 2.0]
1×2 Matrix{Float64}:
1.0 2.0
julia> [1.0, 2.0]
2-element Vector{Float64}:
1.0
2.0
julia> plot([1.0, 2.0],[2.0, 3.0], linewidth=2,legend=:false)
