# Pass optional parameters to model in DifferentialEquations.jl

**URL:** <https://discourse.julialang.org/t/pass-optional-parameters-to-model-in-differentialequations-jl/50718>\
**Category:** Optimization (Mathematical)\
**Tags:** question, diffeq, syntax\
**Created:** [November 24, 2020, 10:36pm UTC](https://discourse.julialang.org/t/pass-optional-parameters-to-model-in-differentialequations-jl/50718 "2020-11-24T22:36:56Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![claudio20497](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/claudio20497/32/36602_2.png) [@claudio20497](https://discourse.julialang.org/u/claudio20497)\
**Post date:** [November 24, 2020, 10:36pm UTC](https://discourse.julialang.org/t/pass-optional-parameters-to-model-in-differentialequations-jl/50718/1 "2020-11-24T22:36:56Z")

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Hello,

I would like to pass optional arguments to a DifferentialEquations.jl ODE model at `ODEProblem` time. Those optional arguments are meant to alter the model without using the `p` argument which I would like to save for calibration parameters.  
So the model would look like this:

```julia

using DifferentialEquations

function model(du,u,p,t ; fixed = [])

### function body  

end;

```

And I would like to get an `ODEProblem` which has that `fixed` parameter set ( e.g. to `[1,2,3]`). Anyway I can’t get anything like:

```julia
problem = ODEProblem(model, u0, t,p; fixed = [1,2,3])

```

to do what I wish.  
Is there a way to accomplish this?

Thanks in advance

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<div class="post-metadata">

**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [November 24, 2020, 11:06pm UTC](https://discourse.julialang.org/t/pass-optional-parameters-to-model-in-differentialequations-jl/50718/2 "2020-11-24T23:06:33Z")

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Just use a closure.

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<div class="post-metadata">

**Author:** ![claudio20497](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/claudio20497/32/36602_2.png) [@claudio20497](https://discourse.julialang.org/u/claudio20497)\
**Post date:** [November 25, 2020, 8:59am UTC](https://discourse.julialang.org/t/pass-optional-parameters-to-model-in-differentialequations-jl/50718/3 "2020-11-25T08:59:51Z")

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Yes, that worked.

Thank you very much for your amazing libraries and continuous support !