## Hearne' method

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bahri
Member
Posts: 33
Joined: Wed May 11, 2016 4:43 am
Vensim version: PLE+

### Hearne' method

Hello,

Can someone please tell how to do "sensitivity analysis"
for a lookup function using a Hearne's method ?

tomfid
Posts: 2508
Joined: Wed May 24, 2006 4:54 am

### Re: Hearne' method

I assume you mean this?
https://onlinelibrary.wiley.com/doi/abs ... 09.00058.x

The paper is paywalled, but I'm going to speculate that in general it would be tricky to implement. You'd have to have a library of functions with desired properties that meet all the reality checks needed for them to make sense in context.

A simple method for doing sensitivity analysis on a lookup is easy, if the lookup is properly normalized to begin with, like:

price = reference price * effect of inventory lookup( inventory / reference inventory )

With this construction, you can already shift and scale the effect using the reference parameters. Then you could add additional distortions of the effect, like:

price = reference price * effect of inventory lookup( inventory / reference inventory ) ^ sensitivity scale

(Bear in mind that this has infinite slope at 0 if scale < 1.)

Or, you could mix two different shapes:

price = reference price * (weight to A*effect of inventory lookup A( inventory / reference inventory )
+ (1-weight to A)*effect of inventory lookup B( inventory / reference inventory ))

bahri
Member
Posts: 33
Joined: Wed May 11, 2016 4:43 am
Vensim version: PLE+

### Re: Hearne' method

Hi Tom,
Yes the link goes to the Hearne's method.
and thanks for other useful description.