[R] nls, nlrq, and box-cox transformation

Johannes Ludsteck johannes.ludsteck at wiwi.uni-regensburg.de
Thu Nov 20 15:02:24 CET 2003

Dear r-help members
I posted this message already yesterday, but don't know whether it
reached you since I joined the group only yesterday.
I would like to estimate the boxcox transformed model
 (y^t - 1)/t ~ b0 + b1 * x.
Unfortunately, R returns with an error message when I try to 
perform this with the call
nls( I((y^t - 1)/t) ~ I(b0 + b1*x),
	start = c(t=1,b0=0,b1=0), data = mydataframe)

The error message is:  Object "t" not found

Apparently R seems not to accept parameters on the left hand
side of a regression model. I know that my do-it-yourself
strategy is not necessary, since the package box-cox is 
available. Unfortunately, I want the use the box-cox 
transformation in a quantile regression, i.e. I have to replace 
nls by nlrq in the call above.

Any suggestions?

Thanks and best regards,
	Johannes Ludsteck
Johannes Ludsteck
Institut fuer Volkswirtschaftslehre
Lehrstuhl Prof. Dr. Moeller
Universitaet Regensburg
Universitaetsstrasse 31
93053 Regensburg
Tel +49/0941/943-2741

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