Chapter 3, Section 3.3

Treatment of Lead Exposed Children Trial (TLC)

Time Plots of Blood Lead Levels 

> library(foreign)

> ds <- read.dta("tlc.dta")

> succ <- subset(ds, ds$trt=="Succimer")

> succimerlong <- reshape(succ, idvar="id", varying=c("y0","y1","y4","y6"), 

+    v.names="y", timevar="time",time=1:4, direction="long")

> attach(succimerlong)

> week <- time

> week[time==1] <- 0

> week[time==2] <- 1

> week[time==3] <- 4

> week[time==4] <- 6

> interaction.plot(week, id, y, ylim=c(0,70), 

+    xlab="Time (in weeks)", ylab="Blood Lead Levels", 

+    main="Time Plot, with Joined Line Segments, of Blood Lead Levels", 

+    col=c(1:50), legend=F)

> interaction.plot(week, trt, y, type="b", pch=19, ylim=c(10, 30), 

+    xlab="Time (in weeks)", ylab="Blood Lead Levels", 

+    main="Plot of Mean Response Profile in the Succimer Group", col=2, legend=F)

Six Cities Study of Air Pollution and Health

Time Plots of Log(FEV1/Height) 

> library(foreign)

> library(lattice)

> ds <- read.dta("fev1.dta")

> fev <- ds[ds$id!=197,]

> attach(fev)

> y <- logfev1 - log(ht)

> xyplot(y ~ age, groups = id, type = "l", xlab="Age (in years)", 

+    ylab="Log(Fev1/Height)", 

+    main="Time plot, with Joined Line Segments, of Log(Fev1/Height) versus Age", 

+    scales=list(x=list(at=c(6,8,10,12,14,16,18)),

+    y=list(at=c(-0.25,0.,0.25,0.50,0.75,1.0))))

> xyplot (y ~ age, groups=id, panel = function(x, y, type, col, lwd)

+    {panel.xyplot(x, y, type = c("p","smooth"), col = "black", lwd=3)}, 

+    xlab = "Age (in years)", ylab = "Log(Fev1/Height)", 

+    main="Time plot of Log(Fev1/Height) versus Age, with Lowess Smoothed Curve", 

+    scales=list(x=list(at=c(6,8,10,12,14,16,18)), 

+    y=list(at=c(-0.25,0.,0.25,0.50,0.75,1.0))))