# Finding indices using "setdiff"?
**URL:** https://discourse.julialang.org/t/finding-indices-using-setdiff/26930
**Category:** New to Julia
**Created:** [July 29, 2019, 9:13am UTC](https://discourse.julialang.org/t/finding-indices-using-setdiff/26930 "2019-07-29T09:13:43Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Ahmed\_Salih](https://discourse.julialang.org/u/Ahmed_Salih)
#### Post date: [July 29, 2019, 9:13am UTC](https://discourse.julialang.org/t/finding-indices-using-setdiff/26930/1 "2019-07-29T09:13:43Z")
Hey guys, say I have these two arrays:
```julia
A = ["1" "2" "3" "4"];
B = ["1" "2" "3" "4" "5" "6"];
```
Then I can use “setdiff” to find the elements which they do not have in common as such:
```julia
C = setdiff(B,A)
2-element Array{String,1}:
"5"
"6"
```
My question is then, would it be possible to get the indices instead? Note the example is string based.
Kind regards
---
### Author:  [@carstenbauer](https://discourse.julialang.org/u/carstenbauer)
#### Post date: [July 29, 2019, 9:23am UTC](https://discourse.julialang.org/t/finding-indices-using-setdiff/26930/2 "2019-07-29T09:23:32Z")
One obvious way would be
```julia
[findfirst(isequal(x), B) for x in setdiff(B,A)]
```
By the way, do you deliberately work with `1xN` matrices instead of column vectors (`A = ["1", "2", "3", "4"];`) ? Typically, the latter is preferable.
---
### Author:  [@Ahmed\_Salih](https://discourse.julialang.org/u/Ahmed_Salih)
#### Post date: [July 29, 2019, 9:25am UTC](https://discourse.julialang.org/t/finding-indices-using-setdiff/26930/3 "2019-07-29T09:25:24Z")
Thanks! It was just an example, usually I also work with column vectors.
Kind regards