# NoiseFunction in DifferentialEquations.jl

**URL:** https://discourse.julialang.org/t/noisefunction-in-differentialequations-jl/39716
**Category:** General Usage
**Tags:** diffeq, sde
**Created:** [May 18, 2020, 7:52pm UTC](https://discourse.julialang.org/t/noisefunction-in-differentialequations-jl/39716 "2020-05-18T19:52:28Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![fernandoduarte](https://avatars.discourse-cdn.com/v4/letter/f/e19b73/32.png) [@fernandoduarte](https://discourse.julialang.org/u/fernandoduarte)
#### Post date: [May 18, 2020, 7:52pm UTC](https://discourse.julialang.org/t/noisefunction-in-differentialequations-jl/39716/1 "2020-05-18T19:52:28Z")

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I am getting the error “NoiseFunction has no field t” when I try to define my own noise process using NoiseFunction in DifferentialEquations.jl following the example in the documentation [here](https://docs.sciml.ai/stable/features/noise_process/#NoiseFunction-Example-1).

Here is the code

```julia
using DiffEqBase, DifferentialEquations, StochasticDiffEq, DiffEqNoiseProcess

f = (u,p,t) -> exp(t)
W = NoiseFunction(0.0,f)
drift(u,p,t) = u
vol(u,p,t) = u
dt = 0.01
tspan = (0.0,1.0)
u0 = 0.0
prob = SDEProblem(drift,vol,u0,(0.0,1.0), noise=W)
sol = solve(prob,dt=0.1)

```

Thanks!

Julia Version 1.4.1 (2020-04-14)  
[DiffEqBase] version = “6.34.2”  
[DifferentialEquations] version = “6.14.0”  
[StochasticDiffEq] version = “6.22.0”  
[DiffEqNoiseProcess] version = “4.1.2”

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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: [May 18, 2020, 8:10pm UTC](https://discourse.julialang.org/t/noisefunction-in-differentialequations-jl/39716/2 "2020-05-18T20:10:33Z")

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Looks like it was missing a test and broke. The fix is here and I’ll get it into our next patch:

> <https://github.com/SciML/StochasticDiffEq.jl/pull/307>
>
> https://discourse.julialang.org/t/noisefunction-in-differentialequations-jl/3971…6

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<div class="post-metadata">

### Author: ![fernandoduarte](https://avatars.discourse-cdn.com/v4/letter/f/e19b73/32.png) [@fernandoduarte](https://discourse.julialang.org/u/fernandoduarte)
#### Post date: [May 18, 2020, 8:50pm UTC](https://discourse.julialang.org/t/noisefunction-in-differentialequations-jl/39716/3 "2020-05-18T20:50:21Z")

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Thank you!