Missing Vensim function LOOKUP AREA

[rogersamso]

Vensim's LOOKUP AREA function is not currently implemented in PySD.

[enekomartinmartinez]

I think about two possible approaches.

The first one would be to use a numerical integration, this may be the easiest one to implement. It may be straightforward with scipy.integrate.quad for floats. But in the case of having dimensions, we need to check if there is something supporting xarray.DataArray inputs.

The other option would be to compute an analytical integration. This is, the LOOKUP AREA function integration should retrieve the x, y pairs from the Lookup object and using the slopes compute the exact area in each section of the lookup.

I currently don't have time to work on this but could help with support.