uups, ok, I see, thanks Tim Calkins wrote: > check the dimensions of your X and P matrices: > >> dim(X) > [1] 21 9 >> dim(P) > [1] 9 21 > > what you see is that the final row is *named* 26. It's actually row 21. > > cheers, > > On 10/29/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: >> Hi All >> >> Maybe I dont understand it, but I would have expected that the design matrix >> has >> as many rows as there were observations available to fit the model. >> Below a small artificial dataset created, then one model fitted and the >> design >> matrix outputted, having 27 rows. Then I delete 6 obs, and fit the model on >> these 21 obs, but the design matrix that comes out has 26 rows? >> >> Thanks for your enlightenment. >> >> Toby >> >> >> >> >> y = c() >> x1 = c() >> x2 = c() >> idx = 1 >> for (i in 1:3) { >> for (j in 1:3) { >> for (k in 1:3) { >> y[idx] = 30*i+10*j+100*i*j+30*k-60 >> x1[idx] = i >> x2[idx] = j >> idx = idx+1 >> } >> } >> } >> >> lm11 = lm(y ~ factor(x1)*factor(x2), x=1) >> summary(lm11) >> unique(predict(lm11)) >> >> X = lm11$x; X >> >> P = solve(t(X)%*%X) %*% t(X); round(P,3) >> >> >> y[3] = NA >> y[6] = NA >> y[12] = NA >> y[18] = NA >> y[24] = NA >> y[27] = NA >> >> lm21 = lm(y ~ factor(x1)*factor(x2), x=1) >> summary(lm21) >> unique(predict(lm21)) >> >> X = lm21$x; X >> >> P = solve(t(X)%*%X) %*% t(X); round(P,3) >> >> ______________________________________________ >> 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.