library(faraway) data(sexab,package="faraway") sexab by(sexab,sexab$csa,summary) plot(ptsd ~ csa, sexab) plot(ptsd ~ cpa, pch=as.character(csa), sexab) t.test(ptsd ~ csa, sexab, var.equal=TRUE) d1 <- ifelse(sexab$csa == "Abused",1,0) d2 <- ifelse(sexab$csa == "NotAbused",1,0) lmod <- lm(ptsd ~ d1 + d2, sexab) sumary(lmod) model.matrix(lmod) lmod <- lm(ptsd ~ d2, sexab) sumary(lmod) lmod <- lm(ptsd ~ d1 + d2 -1, sexab) sumary(lmod) lmod <- lm(ptsd ~ csa, sexab) sumary(lmod) class(sexab$csa) sexab$csa <- relevel(sexab$csa, ref="NotAbused") lmod <- lm(ptsd ~ csa, sexab) sumary(lmod) lmod4 <- lm(ptsd ~ cpa+csa+cpa:csa,sexab) sumary(lmod4) model.matrix(lmod4) plot(ptsd ~ cpa, sexab, pch=as.numeric(csa)) abline(3.96, 0.764) abline(3.96+6.86, 0.764-0.314,lty=2) lmod3 <- lm(ptsd ~ cpa+csa,sexab) sumary(lmod3) plot(ptsd ~ cpa, sexab, pch=as.numeric(csa)) abline(3.98, 0.551) abline(3.98+6.27, 0.551, lty=2) confint(lmod3)[3,] plot(fitted(lmod3),residuals(lmod3),pch=as.numeric(sexab$csa), xlab="Fitted",ylab="Residuals") lmod1 <- lm(ptsd ~ cpa,sexab) sumary(lmod1) data(whiteside,package="MASS") require(ggplot2) ggplot(aes(x=Temp,y=Gas),data=whiteside)+geom_point()+facet_grid(~ Insul)+geom_smooth(method="lm") lmod <- lm(Gas ~ Temp*Insul, whiteside) sumary(lmod) mean(whiteside$Temp) whiteside$ctemp <- whiteside$Temp - mean(whiteside$Temp) lmodc <- lm(Gas ~ ctemp*Insul, whiteside) sumary(lmodc) data(fruitfly,package="faraway") plot(longevity ~ thorax, fruitfly, pch=unclass(activity)) legend(0.63,100,levels(fruitfly$activity),pch=1:5) require(ggplot2) ggplot(aes(x=thorax,y=longevity),data=fruitfly) + geom_point() + facet_wrap( ~ activity) lmod <- lm(longevity ~ thorax*activity, fruitfly) sumary(lmod) model.matrix(lmod) plot(lmod) anova(lmod) lmodp <- lm(longevity ~ thorax+activity, fruitfly) drop1(lmodp,test="F") sumary(lmodp) plot(residuals(lmodp) ~fitted(lmodp),pch=unclass(fruitfly$activity), xlab="Fitted",ylab="Residuals") abline(h=0) lmodl <- lm(log(longevity) ~ thorax+activity, fruitfly) plot(residuals(lmodl) ~ fitted(lmodl),pch=unclass(fruitfly$activity), xlab="Fitted",ylab="Residuals") abline(h=0) sumary(lmodl) exp(coef(lmodl)[3:6]) lmodh <- lm(thorax ~ activity, fruitfly) anova(lmodh) lmodu <- lm(log(longevity) ~ activity, fruitfly) sumary(lmodu) contr.treatment(4) contr.helmert(4) contr.sum(4) contrasts(sexab$csa) <- contr.sum(2) sumary(lm(ptsd ~ csa, sexab))