# Problem 1.23 R

library(ts)

# a.

# read data from a file.

# x <- scan("e:\\Stat207\\Homework\\Ch1\\MASS.dat")

# read data from the class website.

x <- scan("http://www.sci.csueastbay.edu/~esuess/Statistics_6871/Handouts/Handout2/MASS.dat")

win.graph()

par(mfrow=c(2,1))

ts.plot(x)

var(x[100:200])

var(x[400:500])

y <- log(x)

ts.plot(y)

var(y[100:200])

var(y[400:500])

win.graph()

par(mfrow=c(2,1))

hist(x)

hist(y)

#  b.

win.graph()

acf(y)

u <- diff(y)

win.graph()

ts.plot(u)

win.graph()

acf(u)

win.graph()

ts.plot(x[200:300])

# c.

win.graph()

par(mfrow=c(3,2))

ts.plot(x)
acf(x)

ts.plot(y)
acf(y)

ts.plot(u)
acf(u)

# d.

win.graph()

acf(u)