It might be a good idea not to use an outdated version of R.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
>
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