Displaying 3 results from an estimated 3 matches for "photosynthese".
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photosynthesis
2005 Oct 27
1
syntax of nlme with nesting
...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 (depende...
2005 Oct 26
1
help with a self-starting function in nonlinear least squares regression.
...m,
alpha and Rd). I have created this to act as a self-starting function.
The self-starting function seems to work (i.e. when I call "getInitial"
it provides the initial values), but I can't get it to work when used
within "nls". Here is an example:
1)
>
getInitial(Photosynthese~NRhyperbola(Irr,theta,Am,alpha,Rd),data=lit.dat
a[1:11,])
theta Am alpha Rd
0.5021546914 3.7466359015 0.0005743723 -3.0685671752
So, "getInitial" succeeds in extracting the initial values from the
function.
2)
>
nls(Photosynthese~NRh...
2005 Nov 09
0
source of "susbcript out of bounds error" in nmle
...provides, not only the function to be evaluated,
but also estimates of initial values of the parameters that are to be
estimated. I have written a self-starting function (NRhyperbola) for a
non-rectangular hyperbola with 4 parameters (theta, Am, alpha, Rd). The
function works:
>
getInitial(Photosynthese~NRhyperbola(Irr,theta,Am,alpha,Rd),data=lit.dat
a2,na.action=na.omit)
theta Am alpha Rd
0.69495045 35.32201003 0.03156335 1.26873011
If one calls the nlsList function with a grouping variable using
NRhyperbola one gets the parameter estimates for each group:...