[R] x and y coordinates (Rfwdmv Package)

J. Däbritz j.daebritz at freenet.de
Wed Sep 19 11:21:55 CEST 2007


Hello R users,

before asking my question I'd like to stress that I'm an (absolute)
beginner in using R, but enthused about the incredible possibilities of
it.
So I hope my questions are not too stupid.

Here's my problem:

I have a dataset with skewed distributions. In order to obtain approx
multivariate normality by a Box-Cox-Transformation, I used the "Rfwdmv
Package" to estimate a common value of lambda for all the variables.

Therefore I entered the following R commands:
data(my.dat)
l.mle <- fwdtr(my.dat, lambda = 1/3, one.lambda = TRUE)
l.profile.mle <- profile.fwdtr(l.mle)
fwdtrProfilePlot(l.profile.mle)
fwdtrMlePlot(l.mle).

Everything worked well so far and I obtained the plots in question.

The problem is: In these plots I just can see that lambda is roughly
around 1.4, but it could be 1.35 or 1.45 or somewhat in between. The
same problem occurs with the log-likelihoods and the confidence
intervals.

Now my question is:

Is there a possibility obtaining the EXACT log-likelihoods, confidence
intervals and, first of all, lambda values ?

Or more general: How can I obtain the x (or y) value for a specific
(e.g. maximum) y (or x) of a plot in R ?

I would be very grateful if one could give me a lead.

Thank you very much in advance.

With best regards,

Juergen



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