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function rober(du,u,p,t)
  y₁,y₂,y₃ = u
  k₁,k₂,k₃ = p
  du[1] = -k₁*y₁+k₃*y₂*y₃
  du[2] =  k₁*y₁-k₂*y₂^2-k₃*y₂*y₃
  du[3] =  k₂*y₂^2
  nothing
end
prob = ODEProblem(rober,[1.0,0.0,0.0],(0.0,1e5),(0.04,3e7,1e4))</code></pre><p>If we want to get a symbolic representation, we can simply call <code>modelingtoolkitize</code> on the <code>prob</code>, which will return an <code>ODESystem</code>:</p><pre><code class="language-julia">sys = modelingtoolkitize(prob)</code></pre><p>Using this, we can symbolically build the Jacobian and then rebuild the ODEProblem:</p><pre><code class="language-julia">jac = eval(ModelingToolkit.generate_jacobian(sys)[2])
f = ODEFunction(rober, jac=jac)
prob_jac = ODEProblem(f,[1.0,0.0,0.0],(0.0,1e5),(0.04,3e7,1e4))</code></pre></article><nav class="docs-footer"><a class="docs-footer-prevpage" href="../nonlinear/">« Solving Nonlinear Systems with NLsolve</a><a class="docs-footer-nextpage" href="../auto_parallel/">Automated Sparse Parallelism of ODEs via Tracing »</a></nav></div><div class="modal" id="documenter-settings"><div class="modal-background"></div><div class="modal-card"><header class="modal-card-head"><p class="modal-card-title">Settings</p><button class="delete"></button></header><section class="modal-card-body"><p><label class="label">Theme</label></p><div class="select"><select id="documenter-themepicker"><option value="documenter-light">documenter-light</option><option value="documenter-dark">documenter-dark</option></select></div><p></p><hr/><p>This document was generated with <a href="https://github.com/JuliaDocs/Documenter.jl">Documenter.jl</a> on <span class="colophon-date" title="Friday 20 November 2020 14:31">Friday 20 November 2020</span>. Using Julia version 1.4.2.</p></section><footer class="modal-card-foot"></footer></div></div></div></body></HTML>