Just for fun This small program gives negative Sum of Sq in anova (with R versions 2.9.2 and 2.10.0) (linux 32 kernel 2.6.29.6-smp slackware 13.0) : y = c(3.6, 5.0, 5.0, 4.6, 4.5, 4.3, 4.5, 5.1, 4.5, 4.3) trans = as.factor(c("NT","NT","NT","NT","NT","T","T","T","T","T")) lc = lm(y ~ trans) l1 = lm(y ~ 1) anova(l1,lc) # Analysis of Variance Table # # Model 1: y ~ 1 # Model 2: y ~ trans # Res.Df RSS Df Sum of Sq F Pr(>F) # 1 9 1.744 # 2 8 1.744 1 -2.220e-16 # negative Sum of Sq ???? anova(lc) # is OK # 2.9.2 version # Analysis of Variance Table # # Response: y # Df Sum Sq Mean Sq F value Pr(>F) # trans 1 8.214e-32 8.214e-32 3.768e-31 1 # Residuals 8 1.744 0.218 # 2.10.0 version # Analysis of Variance Table # # Response: y # Df Sum Sq Mean Sq F value Pr(>F) # trans 1 0.000 0.000 0 1 # Residuals 8 1.744 0.218
It might be a good idea not to use an outdated version of R. I don't see your "problem" in R 2.12.0. Peter Ehlers On 2010-12-01 05:44, Jean.Coursol at math.u-psud.fr wrote:> Just for fun > > This small program gives negative Sum of Sq in anova (with R versions > 2.9.2 and 2.10.0) (linux 32 kernel 2.6.29.6-smp slackware 13.0) : > > y = c(3.6, 5.0, 5.0, 4.6, 4.5, 4.3, 4.5, 5.1, 4.5, 4.3) > trans = as.factor(c("NT","NT","NT","NT","NT","T","T","T","T","T")) > lc = lm(y ~ trans) > l1 = lm(y ~ 1) > > anova(l1,lc) > > # Analysis of Variance Table > # > # Model 1: y ~ 1 > # Model 2: y ~ trans > # Res.Df RSS Df Sum of Sq F Pr(>F) > # 1 9 1.744 > # 2 8 1.744 1 -2.220e-16 # negative Sum of Sq ???? > > anova(lc) # is OK > > # 2.9.2 version > # Analysis of Variance Table > # > # Response: y > # Df Sum Sq Mean Sq F value Pr(>F) > # trans 1 8.214e-32 8.214e-32 3.768e-31 1 > # Residuals 8 1.744 0.218 > > # 2.10.0 version > # Analysis of Variance Table > # > # Response: y > # Df Sum Sq Mean Sq F value Pr(>F) > # trans 1 0.000 0.000 0 1 > # Residuals 8 1.744 0.218 > > ______________________________________________ > R-help at r-project.org mailing list > stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code.