R commands: ## Read data. fname = "MLCO2MON.DAT" m = matrix(scan(fname,skip=25),ncol=4,byrow=T) ## Perform linear fit to detrend the data. fit = lm(m[,1] ~ m[,2]) ## Save residuals from fit as a time series object. q = ts(fit$residuals,start=c(1974,5),frequency=12) ## Generate the seasonal subseries plot. par(mfrow=c(1,1)) monthplot(q,phase=cycle(q), base=mean, ylab="CO2 Concentrations", main="Seasonal Subseries Plot of CO2 Concentrations", xlab="Month", labels=c("Jan","Feb","Mar","Apr","May","Jun", "Jul","Aug","Sep","Oct","Nov","Dec"))