# @brownian vector?
**URL:** https://discourse.julialang.org/t/brownian-vector/97728
**Category:** Modelling & Simulations
**Created:** [April 21, 2023, 1:07am UTC](https://discourse.julialang.org/t/brownian-vector/97728 "2023-04-21T01:07:06Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@bjarthur](https://discourse.julialang.org/u/bjarthur)
#### Post date: [April 21, 2023, 1:07am UTC](https://discourse.julialang.org/t/brownian-vector/97728/1 "2023-04-21T01:07:06Z")
is there a way to create a vector of brownian variables with [`@brownian`](https://docs.sciml.ai/ModelingToolkit/stable/basics/Variable_metadata/#ModelingToolkit.@brownian-Tuple), much like one can create vectors of regular variables with `@variables`?
```julia
@variables x(t)[1:N] y(t)[1:N] # works
@brownian beta # works
@brownian beta[1:N] # no worky
```
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### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [April 21, 2023, 7:46am UTC](https://discourse.julialang.org/t/brownian-vector/97728/2 "2023-04-21T07:46:40Z")
Not yet. The feature is brand new and not fully complete yet.
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### Author:  [@bjarthur](https://discourse.julialang.org/u/bjarthur)
#### Post date: [April 21, 2023, 12:58pm UTC](https://discourse.julialang.org/t/brownian-vector/97728/3 "2023-04-21T12:58:45Z")
bummer. should i open an issue requesting it as a new feature?
in the meantime, what is the recommended workflow for vectors of SDE’s? is it possible in MTK or do i need to revert to the DiffEq syntax?
specifically, riffing on [this test](https://github.com/SciML/ModelingToolkit.jl/blob/2e53e8947e5761daad95be4aef4f9d1591ee1bb9/test/sdesystem.jl#L588-L612), i’d like to have each of the dependent variables be a vector with each element of `x` getting its own independent additive noise:
```julia
@variables t
D = Differential(t)
sts = @variables x(t)[1:N] y(t)[1:N] z(t)[1:N]
sts_init = [1.0, 0.0, 0.0]
ps = @parameters σ ρ
ps_val = (10.0, 26.0)
@brownian β # [1-N] here?
s = 0.001
β *= s
eqs = [D.(x) .~ σ .* (y .- x) .+ β;
D.(y) .~ x .* (ρ .- z) .- y;
D.(z) .~ x .* y .- z]
@named sys1 = System(eqs, t)
sys1 = structural_simplify(sys1)
prob = SDEProblem(sys1, sts_init, (0.0, 100.0), ps_val)
solve(prob, LambaEulerHeun(), seed = 1)
```
any help would be greatly appreciated. i’m less than a week into learning the SciML ecosystem! thanks.
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### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [April 21, 2023, 1:21pm UTC](https://discourse.julialang.org/t/brownian-vector/97728/4 "2023-04-21T13:21:38Z")
> [@bjarthur](#):
>
> in the meantime, what is the recommended workflow for vectors of SDE’s? is it possible in MTK or do i need to revert to the DiffEq syntax?
For now revert to DiffEq syntax. This piece is still in flux and undocumented and may take a year to evolve.
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### Author:  [@ohaaga](https://discourse.julialang.org/u/ohaaga)
#### Post date: [March 27, 2025, 7:59pm UTC](https://discourse.julialang.org/t/brownian-vector/97728/5 "2025-03-27T19:59:12Z")
Did this ever evolve? Or is there an MTK workaround of any sort? I’d really like to stick error terms on a number of equations that I only know at run-time.
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### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [March 28, 2025, 10:29am UTC](https://discourse.julialang.org/t/brownian-vector/97728/6 "2025-03-28T10:29:15Z")
I’m not sure if this ever got an issue. @cryptic.ax did you ever do anything with this? First step might be to make an issue for it.
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### Author:  [@cryptic.ax](https://discourse.julialang.org/u/cryptic.ax)
#### Post date: [March 28, 2025, 11:35am UTC](https://discourse.julialang.org/t/brownian-vector/97728/7 "2025-03-28T11:35:08Z")
I haven’t done anything with array brownians, but the MWE works now