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st: nonlinear least squares function


From   Jennifer Alix <alix@are.berkeley.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: nonlinear least squares function
Date   Thu, 28 Aug 2003 16:02:35 -0700

Hello,

I am having a lot of trouble programming a (what I perceive as) complicated function to use with the nl command. I can make the command work for simple functions, but alas, life is not simple.
I have data on individuals within communities, and would like to program the function:

sum over i (norm(BXi)*F(BZ1i) + (1-norm(BXi)*F(BZ2i))

where X are variables which determine an individual's probability of being in a certain group and Z1 and Z2 are individual and community characteristics that determine the behaviors of these groups. F() is just some linear function of the Z's. The dependent variable is a community-level observation, so this thing is sort of like an integral over all of the individuals in the community. The main problem is, the number of individuals i varies from community to community, from 10 to 62. Therefore, it seems like I need to build a different function for each community.
Does that make sense? Has anybody encountered a similar problem before? Any hints, suggestions, references, useful prayers to the Stata deity?

Thanks,Jennifer


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