Thanks for the tips. I'll give them a try!

On Sat, Jun 18, 2011 at 12:07 PM, Dennis Murphy <djmuser@gmail.com> wrote:

> Much better..nice!
>
> Dennis
>
> On Sat, Jun 18, 2011 at 1:53 AM, Dimitris Rizopoulos
> <d.rizopoulos@erasmusmc.nl> wrote:
> > maybe another way is by reconstructing the formula using paste(), e.g.,
> >
> > data <- data.frame(y = rnorm(5), x1 = runif(5),
> >    z = runif(5), age = runif(5))
> >
> > nameRsp <- "y"
> > nams <- names(data)
> > namsX <- nams[!nams %in% nameRsp]
> > form <- as.formula(paste(nameRsp, "~" ,
> >    paste("log(", namsX, ")", sep = "", collapse = "+")))
> >
> > lm(form, data)
> >
> >
> > I hope it helps.
> >
> > Best,
> > Dimitris
> >
> >
> > On 6/18/2011 10:41 AM, Dennis Murphy wrote:
> >>
> >> Yes, it's possible, but if you want to do prediction on future
> >> x-values, you will likely have a problem.
> >>
> >> One way to do it would be something like (assuming y is the first column
> >> of dat)
> >>
> >> reg<- lm(y ~ log(as.matrix(dat[, -1])), dat)
> >>
> >> but the output would be pretty ugly (see summary(reg)). Another would
> >> be to construct the matrix outside the data frame and do something
> >> like
> >>
> >> X<- log(as.matrix(dat[, -1]))
> >> reg<- lm(dat$y ~ X)
> >>
> >> There may be better ways, though...
> >>
> >> Dennis
> >>
> >> On Fri, Jun 17, 2011 at 11:08 PM, Scott Fortmann-Roe<scottfr@gmail.com>
> >>  wrote:
> >>>
> >>> Hi,
> >>>
> >>> I would like to do a regression like:
> >>>
> >>>         reg<- lm(y~log(.), data)
> >>>
> >>> where the log function is applied to "." in the form:
> >>>
> >>>        log(x1)+ log(x2)+ log(x3)...
> >>>
> >>> instead of in the form
> >>>
> >>>       log(x1+x2+x3+...)
> >>>
> >>>
> >>> Is this possible?
> >>>
> >>> Thank you,
> >>> Scott
> >>>
> >>>        [[alternative HTML version deleted]]
> >>>
> >>> ______________________________________________
> >>> R-help@r-project.org mailing list
> >>> https://stat.ethz.ch/mailman/listinfo/r-help
> >>> PLEASE do read the posting guide
> >>> http://www.R-project.org/posting-guide.html
> >>> and provide commented, minimal, self-contained, reproducible code.
> >>>
> >>
> >> ______________________________________________
> >> R-help@r-project.org mailing list
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide
> >> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >>
> >
> > --
> > Dimitris Rizopoulos
> > Assistant Professor
> > Department of Biostatistics
> > Erasmus University Medical Center
> >
> > Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
> > Tel: +31/(0)10/7043478
> > Fax: +31/(0)10/7043014
> > Web: http://www.erasmusmc.nl/biostatistiek/
> >
>

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