# Weighting options with Phoenix model

**URL:** <https://forum.certara.com/t/weighting-options-with-phoenix-model/2932>\
**Category:** Modelling and Simulation\
**Created:** [February 3, 2016, 3:42pm UTC](https://forum.certara.com/t/weighting-options-with-phoenix-model/2932 "2016-02-03T15:42:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![cbundgaard](https://avatars.discourse-cdn.com/v4/letter/c/6bbea6/32.png) [@cbundgaard](https://forum.certara.com/u/cbundgaard)\
**Post date:** [February 3, 2016, 3:42pm UTC](https://forum.certara.com/t/weighting-options-with-phoenix-model/2932/1 "2016-02-03T15:42:16Z")

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Hi all,

is it possible to apply weighting shemes when running a Phoenix model? Like the option 1/Yhat or 1/Yhat^2 in the WinNonlin classic platform.

thanks,

Chris

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**Author:** ![SimonDavis](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@SimonDavis](https://forum.certara.com/u/SimonDavis)\
**Post date:** [February 3, 2016, 3:55pm UTC](https://forum.certara.com/t/weighting-options-with-phoenix-model/2932/2 "2016-02-03T15:55:10Z")

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Hi Chris, the simple weighting used in the WNL classic engine to account for residual error is now handled as Eps (epsilon) and to get started you can consider that;

Additive is uniform in classical WinNonlin **(Cpred + eps)**  
Multiplicative is 1/Yhat_Yhat in WNL \_\_(Cpred + Cpred_eps)\_\_  
Power is (Yhat)-2a **(Cpred + Cpreda\*eps)**

**This** has been discussed a few times so using the search function could give you some more examples.

e.g. [http://www.certara.com/forums/topic/251-weighting-in-phoenix-model/?hl=weighting](http://www.certara.com/forums/topic/251-weighting-in-phoenix-model/?hl=weighting)

and [http://www.certara.com/forums/topic/52-model-building-syntax-with-phoenix/?hl=weighting#entry121](http://www.certara.com/forums/topic/52-model-building-syntax-with-phoenix/?hl=weighting#entry121)

among others.

Simon

 ![epsilon.jpg](https://us1.discourse-cdn.com/certara/original/2X/f/ff49c234a2d12d77db133d588281c06dea09d539.jpeg)