# Colinear equations & variables

**URL:** https://forum.dynare.org/t/colinear-equations-variables/20401
**Category:** ML/Bayesian estimation
**Created:** [22 May 2022 12:29 UTC](https://forum.dynare.org/t/colinear-equations-variables/20401 "2022-05-22T12:29:05Z")
**Posts on this page:** 1
**Showing post:** 4

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### Author: ![jpfeifer](https://forum.dynare.org/user_avatar/forum.dynare.org/jpfeifer/32/5044_2.png) [@jpfeifer](https://forum.dynare.org/u/jpfeifer)
#### Post date: [23 May 2022 20:10 UTC](https://forum.dynare.org/t/colinear-equations-variables/20401/4 "2022-05-23T20:10:22Z")

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1. You cannot have more observables than shocks. This would cause stochastic singularity. See [Issue with the Kalman filter - #2 by jpfeifer](https://forum.dynare.org/t/issue-with-the-kalman-filter/18627/2)
2. Without the full codes, it is impossible to tell why the Hessian is not positive definite. Often the `mode_check`-plots provide an indication.
3. The problem with the shock size suggests a wrong data-scaling.

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