Need a numerical solution to simultaneous non-linear equations? The nleqslv package is just what you’re looking for! The coding required is minimal; just define the equations you want solved in a function, set some initial values, and let ‘er rip.
Charlie Park has a nice post describing Tufte’s slopegraphs (old chart, new name).
Kaiser Fung likes these a lot; he’s been calling them Bump charts.
I introduce these to my undergrads when we discuss the paired t test.
Pretty R is a syntax formatter for R, it generates highlighted and properly indented R code suitable for including in an HTML document. Better yet, all the R keywords are linked back to an online reference manual at inside-r.org! Check it out.
# multiple comparison with aov s <- read.table("dogFoodSales.txt",header=T) # fit the ANOVA model and perform post hoc test (Tukey's HSD) print( summary( smodel <- aov(sales ~ location, data=s) ) ) print( TukeyHSD(smodel,"location", ordered=TRUE) ) # check residuals for normality qqnorm(smodel$residuals) qqline(smodel$residuals) print(shapiro.test(smodel$residuals)) # check for homogeneity of variance attach(s) print(bartlett.test(sales ~ location)) # just in case, verify with nonparametric test print(kruskal.test(sales ~ location)) detach(s)