This may appear too elementary to some on this list, but not to me.  My
apologies if this is the case.  I have mastered the lme function but the
nlme function has me stumped.

 

I am attempting to fit a nonlinear mixed model with 4 levels of nesting.
I am getting a cryptic error message and do not know what is wrong with
the syntax of the call.  This is the call:

 

> nlme(Photosynthese~NRhyperbola(Irr,theta,Am,alpha,Rd),

+ fixed=theta+Am+alpha+Rd~1,

+ random=theta~1|Reference/Espece/Plante/Groupe,

+ data=lit.data)

 

NRhyperbola is a self-starting function with one variable (Irr) and four
parameters (theta,Am,alpha,Rd).  The data set (lit.data) contains
Photosynthese (dependent variable) and Irr, as well as the grouping
structure, which is Reference, Espece nested in Reference, Plante nested
in Espece and Groupe nested in Plante.  I want to allow only the
parameter theta to vary randomly.  I get the following error message:
"Error: subscript out of bounds".

 

What does this mean?  There are some "Plante" for which there is only
one "Groupe" , some "Espece" for which there is only one "Plante" etc.
Is this the source of the error?  If so, how can one solve this?

 

Bill Shipley

 


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