# Square decision region model specification - initial evaluation failed

**URL:** <https://discourse.pymc.io/t/square-decision-region-model-specification-initial-evaluation-failed/6413>\
**Category:** Questions\
**Created:** [December 10, 2020, 8:21pm UTC](https://discourse.pymc.io/t/square-decision-region-model-specification-initial-evaluation-failed/6413 "2020-12-10T20:21:38Z")\
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**Author:** ![ricardoV94](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.pymc.io/ricardov94/32/5775_2.png) [@ricardoV94](https://discourse.pymc.io/u/ricardoV94)\
**Post date:** [January 1, 2021, 7:53pm UTC](https://discourse.pymc.io/t/square-decision-region-model-specification-initial-evaluation-failed/6413/3 "2021-01-01T19:53:51Z")

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Have you tried a hard square curve, with just two change points and a p of 0.99 if inside and 0.01 if outside? Two switches should do it. From there you could try adding one sigmoid at a time and hopefully see what is breaking in the full model.

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