Hi James, There is nothing weird at all in your lm() results. You must be aware that the anova table that you are obtaining is a sequential analysis of variance, so when you fit: g1 = lm(z ~ x+y) the sum of squares of x measures the contribution of *x*, after fitting a overall mean (intercept), and the ss of *y*, gives the contribution of *y* after fitting the overall mean and the *x*. These ss are known as type I or sequential sum of squares.- This sequential SS tells you how much the residual sum of squares is reduced by adding a parameter to a model that already contains other factors. So, if you change the order of parameters in your formula, you will obtain different ss. HTH.- Pedro.- -----Mensaje original----- De: bioconductor-bounces at stat.math.ethz.ch [mailto:bioconductor-bounces at stat.math.ethz.ch] En nombre de Wolfgang Huber Enviado el: martes, 12 de diciembre de 2006 10:18 Para: James Anderson CC: bioconductor Asunto: Re: [BioC] silly lm and anova question Dear James, You will need to send a code example that other people can copy/paste, rerun and reproduce. Otherwise you may have very little chance of getting a meaningful answer. Best wishes Wolfgang Huber ------------------------------------------------------------------ Wolfgang Huber EBI/EMBL Cambridge UK http://www.ebi.ac.uk/huber James Anderson wrote: > Hi, > I am using linear model lm and anova. However, I found the following weird phenomenon: > > g1 = lm(z ~ x+y) > g2 = lm(z ~ y+x) > > g1 and g2 have the same linear regression results. However, > anova(g1) and anova(g2) gives very different results in the calculation for sum of square in x and y. the residuals are the same. It looks like a simple question, but I have not figured it out why. > > Many thanks, > James > _______________________________________________ Bioconductor mailing list Bioconductor at stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/bioconductor Search the archives: http://news.gmane.org/gmane.science.biology.informatics.conductor