Sorry, I did not think about the nested design (did not read carefully enough). Another thing to try (untested) is to create a column of 1's and include that specifically and exclude the default intercept, then your column of 1's acts as the intercept, but a p-value is returned from it.
Note that sometimes the other terms may change their definition without an intercept. I had success at one time (quite a while ago, so things could have changed) with specifying the formula as:O Y ~ 1 + x1 + x2 + x3 -1 Which caused it to include the intercept, use that info when setting the dummy vars for x1-x3, then removed the intercept. Again this is all untested, just an idea to try. -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare [EMAIL PROTECTED] (801) 408-8111 > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Sid Kouider > Sent: Friday, August 31, 2007 3:19 PM > To: r-help@stat.math.ethz.ch > Subject: Re: [R] How to obtain intercept statistics in anova > withwithin-subject factors? > > Dear Greg, > Thanks very much for you advice. > Unfortunately, although summary.lm applied on aov objects > indeed shows the intercept's statistics, this function does > not (seem to) work with within-participant designs. As soon > as I enter the info on the error term (see the example in my > first message), then summary.lm(aov_object) crashes ("Error > in if (p == 0) { : argument is of length zero"). > -Sid > > > > > Subject: RE: [R] (no subject) > > Date: Thu, 30 Aug 2007 13:43:19 -0600 > > From: [EMAIL PROTECTED] > > To: [EMAIL PROTECTED]; r-help@stat.math.ethz.ch > > > > Try calling summary.lm on your object (if it is an aov object then > > summary > calls summary.aov which does not show the intercept, but > calling summary.lm directly does give info on the intercept). > > > > -- > > Gregory (Greg) L. Snow Ph.D. > > Statistical Data Center > > Intermountain Healthcare > > [EMAIL PROTECTED] > > (801) 408-8111 > > > > -----Message d'origine----- > > De : Sid Kouider [mailto:[EMAIL PROTECTED] Envoyé : > jeudi 30 août > > 2007 16:54 À : '[EMAIL PROTECTED]' > > Objet : How to obtain intercept statistics in anova with > > within-subject factors? > > > > Dear R users, > > I am looking for an easy (i.e., direct) way of obtaining > the F and p > > values from the intercept in anovas with within-subject designs. > > My data are from a psychophysics experiment where I am using d' (d- > > prime) values obtained from 3 modalities of presentation in each > > subject. I would like to know not only whether there is an > effect of > > modality, but also whether the main effect is significant (meaning > > that d' > 0). > > I know that a t.test again the null mean would provide me > with similar > > stats on the main effect, but I would like to get those > stats in an F > > form, for consistency with the stats on the other factors > of interest. > > > > As far as I understand how R works, the function "anova" > provides you > > with such information but it is restricted to between-group > analyses. > > For within-subject designs, one has to use "summary(aov)" > but stats on > > the intercept are not included in the result of this > function. I have > > pasted an example below. As one can see, only the Sum of Sq > and Mean > > Sq are given for the main effect. > > > > Thank you for any advice you can provide, -Sid > > > > summary(aov(x~mod+Error(suj/(mod)), data=dp)) > > > > Error: suj Df Sum Sq Mean Sq F value Pr(>F) > > Residuals 10 19.5977 1.9598 > > Error: suj:mod > > Df Sum Sq Mean Sq F value Pr(>F) mod > > 2 8.2475 4.1237 4.2955 0.02806 * > > Residuals 20 19.2005 0.9600 > > ---Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 > ' ' 1 Error: > > Within > > Df Sum Sq Mean Sq F value Pr(>F)Residuals 33 55.812 1.691 > > > > ______________________________________________ > R-help@stat.math.ethz.ch 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@stat.math.ethz.ch 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.
