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2006 Mar 01
0
parameterization of gnls model
...o statistically test the influence of several vegetation parameters. The gnls() function in the nlme library seems well-suited for fitting this model, but I am having trouble getting it to converge, even without the autocorrelation structure. Here is the model I'd like to fit: th=eh*((1+theta/thetaref)/(theta/thetaref))^(1/n), where th=true height (dependent variable); eh=estimated height (independent variable); theta is local incidence angle (independent variable); thetaref is fixed; n is the parameter to be estimated. My question is: is this parameterization efficient for gnls()? I've...