[R] formula formatting/grammar for regression

Dieter Menne dieter.menne at menne-biomed.de
Fri Feb 27 20:35:57 CET 2009


BKMooney <bkmooney <at> gmail.com> writes:

> 
> 
> Also, when I tried to use nls, I get an error:  
> nls(ypts ~ exp(xpts))
> Error in getInitial.default(func, data, mCall = as.list(match.call(func,  : 
>   no 'getInitial' method found for "function" objects
> 
> If someone could please point out what I am doing wrong, or point me to a
> good resource on this, I would greatly appreciate it.  

Read the documents on nls. There is not a simple example of the form 
you used on that page, all have a start value, or a special function
to supply the initial values. For all non-linear fitting, you must 
supply reasonably good starting values, for example from a linear 
fit on the log-transformed data.

Dieter



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