# How to extract the indices of a certain variable from a \`Vector{VariableRef}\`?
**URL:** https://discourse.julialang.org/t/how-to-extract-the-indices-of-a-certain-variable-from-a-vector-variableref/113555
**Category:** Optimization (Mathematical)
**Tags:** question, jump, syntax
**Created:** [April 27, 2024, 3:55am UTC](https://discourse.julialang.org/t/how-to-extract-the-indices-of-a-certain-variable-from-a-vector-variableref/113555 "2024-04-27T03:55:49Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@WuSiren](https://discourse.julialang.org/u/WuSiren)
#### Post date: [April 27, 2024, 3:55am UTC](https://discourse.julialang.org/t/how-to-extract-the-indices-of-a-certain-variable-from-a-vector-variableref/113555/1 "2024-04-27T03:55:49Z")
```julia
using JuMP
m = Model()
@variable(m, x[1:3])
@variable(m, y[1:5])
v = all_variables(m)
```
`v` is an `8-element Vector{VariableRef}`. Now I want to extract all the indices with respect to variable `y` from the vector `v` (e.g., it can be a `Vector{Int64}`: `[4:8;]`). How should I do?
Thanks!
---
### Author:  [@odow](https://discourse.julialang.org/u/odow)
#### Post date: [April 27, 2024, 10:27pm UTC](https://discourse.julialang.org/t/how-to-extract-the-indices-of-a-certain-variable-from-a-vector-variableref/113555/2 "2024-04-27T22:27:14Z")
Do something like:
```Julia
julia> using JuMP
julia> model = Model();
julia> @variable(model, x[1:3]);
julia> @variable(model, y[1:5]);
julia> var_to_column = Dict(v => i for (i, v) in enumerate(all_variables(model)))
Dict{VariableRef, Int64} with 8 entries:
y[1] => 4
y[5] => 8
y[2] => 5
x[2] => 2
x[1] => 1
y[4] => 7
x[3] => 3
y[3] => 6
julia> [var_to_column[yi] for yi in y]
5-element Vector{Int64}:
4
5
6
7
8
```
---
### Author:  [@WuSiren](https://discourse.julialang.org/u/WuSiren)
#### Post date: [April 28, 2024, 3:21am UTC](https://discourse.julialang.org/t/how-to-extract-the-indices-of-a-certain-variable-from-a-vector-variableref/113555/3 "2024-04-28T03:21:30Z")
Thanks, @odow ! 🤝 🤝