# DifferentialEquations.jl parameter estimation for less than all states

**URL:** <https://discourse.julialang.org/t/differentialequations-jl-parameter-estimation-for-less-than-all-states/8837>\
**Category:** New to Julia\
**Tags:** question, package, proposal\
**Created:** [February 5, 2018, 4:28pm UTC](https://discourse.julialang.org/t/differentialequations-jl-parameter-estimation-for-less-than-all-states/8837 "2018-02-05T16:28:43Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![moesphere](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/moesphere/32/3348_2.png) [@moesphere](https://discourse.julialang.org/u/moesphere)\
**Post date:** [February 5, 2018, 4:28pm UTC](https://discourse.julialang.org/t/differentialequations-jl-parameter-estimation-for-less-than-all-states/8837/1 "2018-02-05T16:28:43Z")

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When using parameter estimation via the DifferentialEquations.jl package, (how) is it possible to pass the indices of the solution states, for which measurement data is available, to for example the `build_loss_objective`?

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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:** [February 5, 2018, 4:30pm UTC](https://discourse.julialang.org/t/differentialequations-jl-parameter-estimation-for-less-than-all-states/8837/2 "2018-02-05T16:30:50Z")

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It generates the output using the `saveat` at the `t` values. So:

[http://docs.juliadiffeq.org/latest/basics/common\_solver\_opts.html#Output-Control-1](http://docs.juliadiffeq.org/latest/basics/common_solver_opts.html#Output-Control-1)

If you use `save_idxs` to be what indices you want to save at, then it will only save and calculate using those.

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<div class="post-metadata">

**Author:** ![moesphere](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/moesphere/32/3348_2.png) [@moesphere](https://discourse.julialang.org/u/moesphere)\
**Post date:** [February 5, 2018, 4:46pm UTC](https://discourse.julialang.org/t/differentialequations-jl-parameter-estimation-for-less-than-all-states/8837/3 "2018-02-05T16:46:03Z")

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Great and thanks!