# DiffEqArrayOperator is missing

**URL:** <https://discourse.julialang.org/t/diffeqarrayoperator-is-missing/127500>\
**Category:** General Usage\
**Tags:** diffeq\
**Created:** [March 29, 2025, 11:09pm UTC](https://discourse.julialang.org/t/diffeqarrayoperator-is-missing/127500 "2025-03-29T23:09:04Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![ultimatile](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ultimatile/32/216049_2.png) [@ultimatile](https://discourse.julialang.org/u/ultimatile)\
**Post date:** [March 29, 2025, 11:09pm UTC](https://discourse.julialang.org/t/diffeqarrayoperator-is-missing/127500/1 "2025-03-29T23:09:04Z")

</div>

The code below is an example code taken from Problem Types / Non-autonomous Linear ODE / Lie Group Problems section in documentation of DifferentialEquations.jl (I cannot include the link).

```julia
using DifferentialEquations
function update_func(A, u, p, t)
    A[1, 1] = cos(t)
    A[2, 1] = sin(t)
    A[1, 2] = -sin(t)
    return A[2, 2] = cos(t)
end
A = DiffEqArrayOperator(ones(2, 2); update_func=update_func)
prob = ODEProblem(A, ones(2), (10, 50.0))

```

The code cannot run because `DiffEqArrayOperator` is not found.

The error says;

```julia
ERROR: LoadError: UndefVarError: `DiffEqArrayOperator` not defined in `Main`
Stacktrace:
 [1] top-level scope
   @ /path/to/code/test.jl:8
in expression starting at /path/to/code/test.jl:8

```

I haven’t found any package to add besides archived DiffEqOperators.jl.  
Is there anything I have overlooked?

* * *

Julia v0.11.4  
DifferentialEquations v7.16.1

---

<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:** [March 30, 2025, 12:21am UTC](https://discourse.julialang.org/t/diffeqarrayoperator-is-missing/127500/2 "2025-03-30T00:21:58Z")

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> [@ultimatile](#):
>
> I haven’t found any package to add besides archived [DiffEqOperators.jl](https://juliaregistries.github.io/General/packages/redirect_to_repo/DiffEqOperators).  
> Is there anything I have overlooked?

It was archived a long time back in favor of SciMLOperators:

> **[GitHub - SciML/SciMLOperators.jl: SciMLOperators.jl: Matrix-Free Operators for the...](https://github.com/SciML/SciMLOperators.jl)**
>
> SciMLOperators.jl: Matrix-Free Operators for the SciML Scientific Machine Learning Common Interface in Julia

`MatrixOperator` is the version from there:

```julia
using DifferentialEquations
function update_func(A, u, p, t)
    A[1, 1] = cos(t)
    A[2, 1] = sin(t)
    A[1, 2] = -sin(t)
    return A[2, 2] = cos(t)
end
A = MatrixOperator(ones(2, 2); update_func=update_func)
prob = ODEProblem(A, ones(2), (10, 50.0))

```

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<div class="post-metadata">

**Author:** ![ultimatile](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ultimatile/32/216049_2.png) [@ultimatile](https://discourse.julialang.org/u/ultimatile)\
**Post date:** [March 30, 2025, 12:59am UTC](https://discourse.julialang.org/t/diffeqarrayoperator-is-missing/127500/3 "2025-03-30T00:59:34Z")

</div>

Thank you for informing me.

The page Additional Features / DiffEqOperators is also still present.  
This is one reason I failed to notice that this function has been deprecated.  
I mistakenly searched for `DiffEqArrayOperator` in SciMLOperators.jl.

---

<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:** [March 30, 2025, 4:42pm UTC](https://discourse.julialang.org/t/diffeqarrayoperator-is-missing/127500/4 "2025-03-30T16:42:08Z")

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Oh thanks, it looks like one doc missed the updates. I’ll fix that up today