# Time-plotting the derivative of a species (reaction velocity) in catalyst

**URL:** <https://discourse.julialang.org/t/time-plotting-the-derivative-of-a-species-reaction-velocity-in-catalyst/129927>\
**Category:** Chemistry\
**Tags:** catalyst\
**Created:** [June 16, 2025, 1:47pm UTC](https://discourse.julialang.org/t/time-plotting-the-derivative-of-a-species-reaction-velocity-in-catalyst/129927 "2025-06-16T13:47:03Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Andre\_Renard](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/andre_renard/32/217339_2.png) [@Andre\_Renard](https://discourse.julialang.org/u/Andre_Renard)\
**Post date:** [June 16, 2025, 1:47pm UTC](https://discourse.julialang.org/t/time-plotting-the-derivative-of-a-species-reaction-velocity-in-catalyst/129927/1 "2025-06-16T13:47:03Z")

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Hello,  
I can’t find an easy way to time-plot a derivative of a species, although I’m sure data are stored somewhere. Thanks for help.  
Andre

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**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:** [June 16, 2025, 9:37pm UTC](https://discourse.julialang.org/t/time-plotting-the-derivative-of-a-species-reaction-velocity-in-catalyst/129927/2 "2025-06-16T21:37:32Z")

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`sol(t, Val{1})` is how it’s stored in the solution. ``sol(t, Val{1}; idxs = A)` for species`A`. You can interpolate with a dense `t` to then make the plot.