# Run only the algebraic part of the solver

**URL:** https://discourse.julialang.org/t/run-only-the-algebraic-part-of-the-solver/128803
**Category:** Modelling & Simulations
**Tags:** question, ode, modelingtoolkit, dae
**Created:** [May 7, 2025, 3:04pm UTC](https://discourse.julialang.org/t/run-only-the-algebraic-part-of-the-solver/128803 "2025-05-07T15:04:11Z")
**Posts on this page:** 1
**Showing post:** 15

<div class="post-metadata">

### Author: ![baggepinnen](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/baggepinnen/32/693_2.png) [@baggepinnen](https://discourse.julialang.org/u/baggepinnen)
#### Post date: [May 9, 2025, 10:42am UTC](https://discourse.julialang.org/t/run-only-the-algebraic-part-of-the-solver/128803/15 "2025-05-09T10:42:57Z")

</div>

Since you have an input-output system, I’m not sure the package you link is the most suitable. See [Home · RobustAndOptimalControl Documentation](https://juliacontrol.github.io/RobustAndOptimalControl.jl/dev/#Model-reduction) for model-order reduction of linear statespace systems with inputs, in particular, try

```julia
using ControlSystemsBase
sys = ss(matrices...)
baltrunc(sys, residual=true)
baltrunc(sys, n=desired_state_dimension, residual=true)

```

or

```julia
using RobustAndOptimalControl
using DSP
w1 = 1e-4 # Lower frequency limit
w2 = 1e1 # upper
fc = DSP.analogfilter(DSP.Bandpass(w1, w2), DSP.Butterworth(2))
tfc = DSP.PolynomialRatio(fc)
W = tf(DSP.coefb(tfc), DSP.coefa(tfc))
rsys, hs = frequency_weighted_reduction(sys, W, 1)

```

for a reduction that focuses on a particular frequency range

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