[R] Complicated nls formula giving singular gradient message
davef at otter-rsch.com
Tue Dec 14 01:37:19 CET 2010
I always enjoy these direct comparisons between different software packages.
I coded this up in AD Model Builder which is freely available at
http://admb-project.org ADMB calculates exact derivatives via automatic
differentiation so it tends to be more stable for these difficult problems.
The parameter estimates are
# Number of parameters = 3
Objective function value = 307873. Maximum gradient component = 1.45914e-06
The objective function is just least squares.
So it looks like SAS did pretty well before dying.
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