# How do I use an arugment to a function that is either a vector or a 1D view

**URL:** <https://discourse.julialang.org/t/how-do-i-use-an-arugment-to-a-function-that-is-either-a-vector-or-a-1d-view/94342>\
**Category:** New to Julia\
**Tags:** question, views\
**Created:** [February 9, 2023, 12:40pm UTC](https://discourse.julialang.org/t/how-do-i-use-an-arugment-to-a-function-that-is-either-a-vector-or-a-1d-view/94342 "2023-02-09T12:40:13Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Thomas\_Van\_Giel](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/thomas_van_giel/32/46737_2.png) [@Thomas\_Van\_Giel](https://discourse.julialang.org/u/Thomas_Van_Giel)\
**Post date:** [February 9, 2023, 12:40pm UTC](https://discourse.julialang.org/t/how-do-i-use-an-arugment-to-a-function-that-is-either-a-vector-or-a-1d-view/94342/1 "2023-02-09T12:40:13Z")

</div>

I have a simulation which is given by a t x N matrix abundances\_timeseries, where t is the timestep and N the amount of variables. (This can for example be a 10^3 x 5 matrix).

I want to check for oscillating behaviour by comparing if the value at the last timestep equals the values at some earlier timestep. I do this with the following (simplified here) code:

```julia
using Random
# generate random abundances_timeseries. Usually this is not random but 
# from a simulation
abundances_timeseries = rand(1:100, (10000, 5))
# n_final is the final value of all the variables in the simulation
n_final = abundances_timeseries[:, t_max]

for t in t_max:-1:1
    n_t = abundances_timeseries[:, t]
    if is_similar(n_t, n_final)
       println("the system is oscillating")
    end
end

function is_similar(n1::Vector{<:Real}, n2::Vector{<:Real})
    if length(n1) != length(n2)
        return false
    end
    N = length(n1)
    for i in 1:N
        if !is_similar(n1[i], n2[i])
            return false
        end
    end
    return true
end

function is_similar(ni::Real, nj::Real)
    cutoff = 0.99
    if cutoff*ni <= nj <= ni/cutoff
        return true
    end
    return false
end

```

This works fine, but I want to use @view for n\_final and n\_t for performance reasons, but I still want the code to work for regular vectors as well. If I change them to views I get the error:

```julia
ERROR: MethodError: no method matching is_similar(::Vector{Float64}, ::SubArray{Float64, 1, Matrix{Float64}, Tuple{Base.Slice{Base.OneTo{Int64}}, Int64}, true})
Closest candidates are:
  is_similar(::Vector{<:Real}, ::Vector{<:Real})

```

Is there a sort of common type I can assign to n1 and n2 in my is\_similar function to work on both? Or is the only way to use  
`Union{Vector{<:Real}, ::SubArray{Float64, 1, Matrix{Float64}, Tuple{Base.Slice{Base.OneTo{Int64}}, Int64}, true})}`?

---

<div class="post-metadata">

**Author:** ![ademonts](https://avatars.discourse-cdn.com/v4/letter/a/ba8739/32.png) [@ademonts](https://discourse.julialang.org/u/ademonts)\
**Post date:** [February 9, 2023, 12:47pm UTC](https://discourse.julialang.org/t/how-do-i-use-an-arugment-to-a-function-that-is-either-a-vector-or-a-1d-view/94342/2 "2023-02-09T12:47:53Z")

</div>

Use `::AbstractVector` instead of `::Vector`.

---

<div class="post-metadata">

**Author:** ![Thomas\_Van\_Giel](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/thomas_van_giel/32/46737_2.png) [@Thomas\_Van\_Giel](https://discourse.julialang.org/u/Thomas_Van_Giel)\
**Post date:** [February 9, 2023, 12:59pm UTC](https://discourse.julialang.org/t/how-do-i-use-an-arugment-to-a-function-that-is-either-a-vector-or-a-1d-view/94342/3 "2023-02-09T12:59:10Z")

</div>

This works, thank you!