# Append an array inside a function
**URL:** https://discourse.julialang.org/t/append-an-array-inside-a-function/49289
**Category:** General Usage
**Created:** [October 30, 2020, 7:19am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289 "2020-10-30T07:19:59Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@Nova](https://discourse.julialang.org/u/Nova)
#### Post date: [October 30, 2020, 7:19am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289/1 "2020-10-30T07:19:59Z")
I don’t really understand the scope of the variable SV here. I used it inside a function, so I expect that when I add elements to it, it should work fine:
```julia
SV = rand(10, 1)
function add_star(SV)
for i =1:5
append!(SV_new[:,1], 4)
end
return SV[:,1]
end
```
I am expecting the output of the function to be an array with 15 elements where the last 5 elements are 4, but the output is still an array with 10 elements, why?
---
### Author:  [@mauro3](https://discourse.julialang.org/u/mauro3)
#### Post date: [October 30, 2020, 7:26am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289/2 "2020-10-30T07:26:06Z")
`SV[:,1]` returns a new array. Instead you need to do `@view(SV[:,1])`, to get a view.
---
### Author:  [@Nova](https://discourse.julialang.org/u/Nova)
#### Post date: [October 30, 2020, 7:33am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289/3 "2020-10-30T07:33:28Z")
Sorry that was a mistake. The correct code is:
```julia
function add_star(SV)
for i =1:5
append!(SV[:,1], 4)
end
return SV[:,1]
end
```
---
### Author:  [@GunnarFarneback](https://discourse.julialang.org/u/GunnarFarneback)
#### Post date: [October 30, 2020, 8:00am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289/4 "2020-10-30T08:00:26Z")
Chances are, especially if you have a Matlab background, that you rather want a vector than a one-column matrix, in which case this is simply
```julia
SV = rand(10)
function add_star(SV)
for i = 1:5
append!(SV, 4)
end
return SV
end
```
If you really want a matrix you have to go through some hoops to achieve the same thing.
---
### Author:  [@Nova](https://discourse.julialang.org/u/Nova)
#### Post date: [October 30, 2020, 8:16am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289/5 "2020-10-30T08:16:44Z")
But this doesn’t work. The output of the function is still an array with 10 elements.
---
### Author:  [@fredrikekre](https://discourse.julialang.org/u/fredrikekre)
#### Post date: [October 30, 2020, 8:39am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289/6 "2020-10-30T08:39:40Z")
No it has appened 5 4s:
```julia
julia> SV = rand(10);
julia> function add_star(SV)
for i = 1:5
append!(SV, 4)
end
return SV
end
add_star (generic function with 1 method)
julia> add_star(SV);
julia> SV
15-element Array{Float64,1}:
0.7833650176317701
0.5668846033320463
0.4391438535780501
0.1708544616711889
0.5183882750256887
0.039540666370839306
0.9220275850039967
0.2936365813778392
0.6266212769148911
0.7356570139131633
4.0
4.0
4.0
4.0
4.0
```
Note though, for single element additions you should use `push!` instead of `append!`.
---
### Author:  [@DNF](https://discourse.julialang.org/u/DNF)
#### Post date: [October 30, 2020, 8:49am UTC](https://discourse.julialang.org/t/append-an-array-inside-a-function/49289/7 "2020-10-30T08:49:23Z")
There are two issues:
Every time you slice, you create a copy, so each `SV[:, 1]` inside the loop creates a new copy, and the `SV[:, 1]` in the return statement also creates a copy, and they are all different. So you have
```julia
for i in 1:5
create copy of array
append 4 to this copy
forget the copy, the original array has not been modifieed
end
make another copy of the original unmodified array and return it
```
The second issue is that you cannot append or push scalars to a matrix, only to vectors. `rand(10, 1)` is a 2-dimensional array/matrix. You need to work with vectors, so it should be `SV = rand(10)`. If you are coming from Matlab, this is a very common point of confusion. Matlab users tend to use `rand(N, 1)`, `zeros(N, 1)`, `ones(N, 1)` all over the place. You’ll have to rid yourself of that habit 😉