# How to evaluate(substitute numerical values of params n states) a jacobian in modelingtoolkit using generate\_jacobian or calculate\_jacobian?

**URL:** <https://discourse.julialang.org/t/how-to-evaluate-substitute-numerical-values-of-params-n-states-a-jacobian-in-modelingtoolkit-using-generate-jacobian-or-calculate-jacobian/71466>\
**Category:** General Usage\
**Tags:** modelingtoolkit\
**Created:** [November 14, 2021, 9:55pm UTC](https://discourse.julialang.org/t/how-to-evaluate-substitute-numerical-values-of-params-n-states-a-jacobian-in-modelingtoolkit-using-generate-jacobian-or-calculate-jacobian/71466 "2021-11-14T21:55:40Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![yewalenikhil65](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yewalenikhil65/32/26873_2.png) [@yewalenikhil65](https://discourse.julialang.org/u/yewalenikhil65)\
**Post date:** [November 14, 2021, 9:55pm UTC](https://discourse.julialang.org/t/how-to-evaluate-substitute-numerical-values-of-params-n-states-a-jacobian-in-modelingtoolkit-using-generate-jacobian-or-calculate-jacobian/71466/1 "2021-11-14T21:55:40Z")

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i found that `ModelingToolkit.calculate_jacobian()` function symbolically generates Jacobian of ODESystem in MTK docs.  
How does one substitute numerical values of parameters and state varables numerical values in this matrix to evaluate ?

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**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:** [November 15, 2021, 5:37am UTC](https://discourse.julialang.org/t/how-to-evaluate-substitute-numerical-values-of-params-n-states-a-jacobian-in-modelingtoolkit-using-generate-jacobian-or-calculate-jacobian/71466/2 "2021-11-15T05:37:22Z")

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Try `Symbolics.substitute`

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**Author:** ![yewalenikhil65](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yewalenikhil65/32/26873_2.png) [@yewalenikhil65](https://discourse.julialang.org/u/yewalenikhil65)\
**Post date:** [November 15, 2021, 5:41am UTC](https://discourse.julialang.org/t/how-to-evaluate-substitute-numerical-values-of-params-n-states-a-jacobian-in-modelingtoolkit-using-generate-jacobian-or-calculate-jacobian/71466/3 "2021-11-15T05:41:47Z")

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thanks @baggepinnen  
i am doing currently following

```julia
x₀map = states(odesys) .=> x0
pmap = parameters(odesys) .=> ps
jac = substitute.( ModelingToolkit.calculate_jacobian(odesys), (Dict([x₀map;pmap]),) )
jac = Symbolics.value.(jac)

```

Hope i am doing this right!

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**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:** [November 15, 2021, 8:00am UTC](https://discourse.julialang.org/t/how-to-evaluate-substitute-numerical-values-of-params-n-states-a-jacobian-in-modelingtoolkit-using-generate-jacobian-or-calculate-jacobian/71466/4 "2021-11-15T08:00:21Z")

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Looks about right to me, just make sure the states and parameters are returned in the order you expect. 😃