######## # Module 11 ## Property Tax data # 1. Using your numeric lot size variable created from module 10, # compute the Spearman correlation between lot size and cityTax # among those houses that are primary residences # (pick up the data where you left off) cor(tax2\$sqft, tax2\$cityTax, method="spearman",use="complete") ### note spearman is rank-based/non-parametric cor(log10(tax2\$sqft), log10(tax2\$cityTax), method="spearman",use="complete") cor(log10(tax2\$sqft), tax2\$cityTax, method="spearman",use="complete") # example of using with() with(tax2, cor(sqft, cityTax, method="spearman",use="complete")) # 2. Fit a regression model with cityTax as the outcome - what # is the coefficient for lot size, as well as its t-statistic # and p-value? How much do these metrics change if you # transform the variables (e.g. log10) f = lm(cityTax ~ sqft, data=tax2) summary(f)\$coef[2,c(1,3,4)] fl = lm(log10(cityTax+1) ~ log10(sqft+1), data=tax2) summary(fl)\$coef[2,c(1,3,4)] plot(log10(tax2\$sqft+1),log10(tax2\$cityTax+1)) ########### # Download: 'http://biostat.mc.vanderbilt.edu/wiki/pub/Main/DataSets/cdystonia.sav' # And then place in your working directory # load("cdystonia.sav") # codebook: http://biostat.mc.vanderbilt.edu/wiki/pub/Main/DataSets/Ccdystonia.html # Randomized to placebo (N=36), 5000 units of BotB (N=36), # 10,000 units of BotB (N=37) # Response variable: total score on Toronto Western Spasmodic Torticollis Rating # Scale (TWSTRS), measuring severity, pain, and disability of cervical dystonia # (high scores mean more impairment) # TWSTRS measured at baseline (week 0) and weeks 2, 4, 8, 12, 16 # after treatment began # 3. Visualize data using lattice or ggplot2 library(lattice) xyplot(twstrs ~ week | site, data=cdystonia,type="l") xyplot(twstrs ~ week | id, data=cdystonia,type="l")