# Could Someone Guide me on Issue with Array Indexing in Julia?

**URL:** <https://discourse.julialang.org/t/could-someone-guide-me-on-issue-with-array-indexing-in-julia/113897>\
**Category:** Performance\
**Created:** [May 6, 2024, 11:10am UTC](https://discourse.julialang.org/t/could-someone-guide-me-on-issue-with-array-indexing-in-julia/113897 "2024-05-06T11:10:37Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![rich20509](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rich20509/32/208942_2.png) [@rich20509](https://discourse.julialang.org/u/rich20509)\
**Post date:** [May 6, 2024, 11:10am UTC](https://discourse.julialang.org/t/could-someone-guide-me-on-issue-with-array-indexing-in-julia/113897/1 "2024-05-06T11:10:37Z")

</div>

Hello there,

This is my code:  
Julia code demonstrating the issue  
x = [1, 2, 3, 4, 5]  
y = x[1:3]

Now let’s try to modify y  
y[1] = 10

println("x: ", x)  
println("y: ", y)

I am encountering an unexpected behavior while working with array indexing in Julia. In the code snippet above, I’m trying to create a new array y by indexing elements 1 to 3 from array x. However, when I modify an element of y, I notice that the corresponding element in x is also modified, which is unexpected behavior to me.

I would expect x to remain unchanged after modifying y.

Also, I have gone through this: [https://discourse.julialang.org/t/please-someone-explain-me-the-array-indexing-example-from-manual/110174](https://discourse.julialang.org/t/please-someone-explain-me-the-array-indexing-example-from-manual/110174)[devops](https://www.igmguru.com/cloud-computing/devops-certification-training/) which definitely helped me out a lot

Could someone please explain why this is happening and suggest how I can achieve my desired behavior?

Thankyou in advance for your help and assistance.

---

<div class="post-metadata">

**Author:** ![screw\_dog](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/screw_dog/32/48119_2.png) [@screw\_dog](https://discourse.julialang.org/u/screw_dog)\
**Post date:** [May 6, 2024, 11:13am UTC](https://discourse.julialang.org/t/could-someone-guide-me-on-issue-with-array-indexing-in-julia/113897/2 "2024-05-06T11:13:41Z")

</div>

This shouldn’t happen, and doesn’t happen for me.

```julia
x = [1, 2, 3, 4, 5]
5-element Vector{Int64}:
 1
 2
 3
 4
 5

julia> y = x[1:3]
3-element Vector{Int64}:
 1
 2
 3

julia> y[1] = 10
10

julia> x
5-element Vector{Int64}:
 1
 2
 3
 4
 5

```

To get the behaviour you describe usually requires either a `y = x` assignment, or using the `@view`/`@views` macro (or `view` function).