Dear Ashim, I’ll address your questions briefly but they’re really not appropriate for this list, which is for questions about using R, not general statistical questions.
(1) The relevant distribution is within cells of the wool x tension cross-classification because it’s the deviations from the cell means that are supposed to be normally distributed with equal variance. In the warpbreaks data there are only 9 cases per cell. If you examine all of these deviations simultaneously, that’s equivalent to examining the residuals from the two-way ANOVA model fit to the data. (2) Yes, (d) and (e) visualize simple effects, and (a) and (b) visualize main effects, the latter only because the data are balanced. Best, John ------------------------------------- John Fox, Professor Emeritus McMaster University Hamilton, Ontario, Canada Web: http://socserv.mcmaster.ca/jfox/ On 2018-01-09, 10:18 AM, "Ashim Kapoor" <ashimkap...@gmail.com> wrote: >Dear Sir, > > >Many thanks for your reply. > > >I have a query. > > > >I have a whole set of distributions which should be made normal / >homoscedastic. Take for instance the warpbreaks data set. > > > >We have the following boxplots for the warpbreaks dataset: > > >a. boxplot(breaks ~ wool) > >b. boxplot(breaks ~ tension) > >c. boxplot(breaks ~ interaction(wool,tension)) >d. boxplot(breaks ~ wool @ each level of tension) >e. boxplot(breaks ~ tension @ each level of wool) > > >Now should we not be making a-e normal and homoscedastic? Should we not >make a giant collection of boxplots from a-e and use the SpreadLevelPlot >on this entire collection? > > >A second query : (d) and (e) are the distribution of the simple effects >of factor wool and tension @ each level of the other. Is that correct? >Are (a) and (b) the distribution of the main effect of wool and tension? >Please confirm. > > > >Best Regards, >Ashim > > > > > > > > > >On Sun, Jan 7, 2018 at 8:05 PM, Fox, John ><j...@mcmaster.ca> wrote: > >Dear Ashim, > >Try spreadLevelPlot(breaks ~ interaction(tension, wool), data=warpbreaks) >. > >I hope this helps, > John > >----------------------------- >John Fox, Professor Emeritus >McMaster University >Hamilton, Ontario, Canada >Web: >socialsciences.mcmaster.ca/jfox/ <http://socialsciences.mcmaster.ca/jfox/> > > > >> -----Original Message----- >> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Ashim >> Kapoor >> Sent: Sunday, January 7, 2018 12:08 AM >> To: r-help@r-project.org >> Subject: [R] SpreadLevelPlot for more than one factor >> >> Dear All, >> >> I want a transformation which will make the spread of the response at >>all >> combinations of 2 factors the same. >> >> See for example : >> >> boxplot(breaks ~ tension * wool, warpbreaks) >> >> The closest I can do is : >> >> spreadLevelPlot(breaks ~tension , warpbreaks) spreadLevelPlot(breaks ~ >>wool , >> warpbreaks) >> >> I want to do : >> >> spreadLevelPlot(breaks ~tension * wool, warpbreaks) >> >> But I get : >> >> > spreadLevelPlot(breaks ~tension * wool , warpbreaks) >> Error in spreadLevelPlot.formula(breaks ~ tension * wool, warpbreaks) : >> right-hand side of model has more than one variable >> >> What is the corresponding appropriate function for 2 factors ? >> >> Many thanks, >> Ashim >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> >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- <http://www.R-project.org/posting-> >> guide.html >> and provide commented, minimal, self-contained, reproducible code. > > > > > ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
