Thank you! But could you please explain why the 2nd formula is a model to avoid? Thanks again! On Tue, Jun 5, 2012 at 6:18 PM, Peter Ehlers <ehl...@ucalgary.ca> wrote:
> You mention 3 models. In all of them, the '-1' simply removes > the intercept term; help('formula') explains the use of '-' > in general. > > 1. lm(y~ x * w - 1) is clearly explained in help('formula'); > 2. lm(y~ x:w - 1) ditto (and this is a model to avoid); > 3. lm(y~ x/w - 1) this is equivalent to lm(y~ x + w %in% x - 1) > where the %in% operator is explained in help('formula'). A good > and simple example is found in the MASS book (chapter 6) the code > for which is available in the 'Scripts' subfolder of library/MASS > of your R installation. > > Peter Ehlers > > > > On 2012-06-05 13:58, Michael wrote: > >> I read your website but still don't know the difference between the >> three >> formulas... >> >> Thank you! >> >> On Mon, Jun 4, 2012 at 11:14 PM, Joshua Wiley<jwiley.ps...@gmail.com>** >> wrote: >> >> Hi Michael, >>> >>> This is far from exhaustive (I wrote it as an introduction some years >>> ago) but you may find it useful to start: >>> https://joshuawiley.com/R/**formulae_in_R.aspx<https://joshuawiley.com/R/formulae_in_R.aspx> >>> >>> Cheers, >>> >>> Josh >>> >>> On Mon, Jun 4, 2012 at 9:06 PM, Michael<comtech....@gmail.com> wrote: >>> >>>> Hi all, >>>> >>>> Could you please point me to good materials on various >>>> tricks/intuitions/techniques of regression, and hopefully in R? >>>> >>>> For example, what does lm(y~ x * w - 1) mean vs. lm(y ~ x/w -1 ) vs. lm >>>> >>> (y >>> >>>> ~ x:w-1), etc... >>>> >>>> I just found that even simple linear regression is not that simple and >>>> there are a lot of tricks/techniques in using them... >>>> >>>> Hopefully I can find good materials on these! >>>> >>>> Thank you! >>>> >>>> [[alternative HTML version deleted]] >>>> >>>> ______________________________**________________ >>>> R-help@r-project.org mailing list >>>> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help> >>>> PLEASE do read the posting guide >>>> >>> http://www.R-project.org/**posting-guide.html<http://www.r-project.org/posting-guide.html> >>> <http://www.**r-project.org/posting-guide.**html<http://www.r-project.org/posting-guide.html>> >>> >>> >>> and provide commented, minimal, self-contained, reproducible code. >>>> >>> >>> >>> >>> -- >>> Joshua Wiley >>> Ph.D. Student, Health Psychology >>> Programmer Analyst II, Statistical Consulting Group >>> University of California, Los Angeles >>> https://joshuawiley.com/ >>> >>> >> [[alternative HTML version deleted]] >> >> ______________________________**________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help> >> PLEASE do read the posting guide http://www.R-project.org/** >> posting-guide.html <http://www.r-project.org/posting-guide.html> >> and provide commented, minimal, self-contained, reproducible code. >> > > [[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.