[R-sig-dyn-mod] Fitting parameters in a Verlhust population growth model

[Thomas Petzoldt]

Hello Jose,

this looks indeed like the typical order-of-magnitude-problem. Have you 
already tried to rescale the parameters? Section 2.4.3 in the 
"simecol-Howto" vignette explains how this can be done.

The vignette is included in the package, but can also be found online:

http://cran.r-project.org/web/packages/simecol/vignettes/b-simecol-howtos.pdf

The following seems to work:

resultado <- fitOdeModel(verlhust,
                          obstime=censo$ano,
                          yobs=subset(censo,select=poblacion),
                          fn=ssqOdeModel,
                          initialize=FALSE,
                          method="PORT", scale=c(1/0.01, 1/1e8),
                          lower=c(alfa=0,L=0))



Note also that setting solver="ode" speeds up by about 50%.

Thomas P.