You may try the following to perform anova: anova(lm(y~x)) or summary(aov(y~x))
2011/4/13 Ubuntu Diego <ubuntu.di...@gmail.com> > Hi all, > I have a very easy questions (I hope). I had measure a property of > plants, growing in three different substrates (A, B and C). The rest of the > conditions remained constant. There was very high variation on the results. > I want to do address, whether there is any difference in the > response (my measurement) from substrate to substrate? > > x<-c('A','A','A','A','A','B','B','B','B','B','C','C','C','C','C') # > Substrate type > y <- c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15) # Results of the measurement > MD<-data.frame(x,y) > > I wrote a linear model for this: > > summary(lm(y~x,data=MD)) > > This is the output: > > Call: > lm(formula = y ~ x, data = MD) > > Residuals: > Min 1Q Median 3Q Max > -2.000e+00 -1.000e+00 5.551e-17 1.000e+00 2.000e+00 > > Coefficients: > Estimate Std. Error t value Pr(>|t|) > (Intercept) 3.0000 0.7071 4.243 0.001142 ** > xB 5.0000 1.0000 5.000 0.000309 *** > xC 10.0000 1.0000 10.000 3.58e-07 *** > --- > Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1 > > Residual standard error: 1.581 on 12 degrees of freedom > Multiple R-squared: 0.8929, Adjusted R-squared: 0.875 > F-statistic: 50 on 2 and 12 DF, p-value: 1.513e-06 > > I conclude that there is an effect of substrate type (x). > NOW the questions : > 1) Do the fact that the all p-values are significant means > that all the groups are different from each other ? > 2) Is there a (easy) way to plot, mean plus/minus 2*sd for > each substrate type ? (with asterisks denoting significant differences ?) > > > THANKS ! > > version > platform x86_64-apple-darwin9.8.0 > arch x86_64 > os darwin9.8.0 > system x86_64, darwin9.8.0 > status > major 2 > minor 11.1 > year 2010 > month 05 > day 31 > svn rev 52157 > language R > version.string R version 2.11.1 (2010-05-31) > > ______________________________________________ > 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. > [[alternative HTML version deleted]]
______________________________________________ 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.