# Defining and input signal for a differential equation

**URL:** <https://discourse.julialang.org/t/defining-and-input-signal-for-a-differential-equation/23703>\
**Category:** New to Julia\
**Tags:** question, diffeq\
**Created:** [April 30, 2019, 3:30pm UTC](https://discourse.julialang.org/t/defining-and-input-signal-for-a-differential-equation/23703 "2019-04-30T15:30:02Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![stevengj](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stevengj/32/71_2.png) [@stevengj](https://discourse.julialang.org/u/stevengj)\
**Post date:** [April 30, 2019, 3:41pm UTC](https://discourse.julialang.org/t/defining-and-input-signal-for-a-differential-equation/23703/2 "2019-04-30T15:41:55Z")

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See this previous discussion:

> [@How to use DifferentialEquations with complicated equations](https://discourse.julialang.org/t/how-to-use-differentialequations-with-complicated-equations/20740/3):
>
> You can always pass additional parameters to a functional interface by using lexical scoping. (This seems to be a FAQ for libraries that do integration, optimization, root-finding, etcetera.) For example, the [QuadGK package](https://github.com/JuliaMath/QuadGK.jl) package lets you integrate a function of the form f(x) via quadgk(x, a, b). But suppose you have a function g(x, α, β) that depends on two additional parameters α,β — does that mean you can’t use it with QuadGK, unless you rewrite it to use global variables? No! You…

Short answer: the default approach is to use a closure for something like this

```julia
neural_ode((h,t) -> dhdt(h,x,t), h, tspan, Tsit5(), saveat=t,reltol=1e-7,abstol=1e-9)

```

but the DifferentialEquations package also supports passing additional parameters explicitly to ease sensitivity analysis.

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