library(prettyR)
ch2_1<-scan("http://kanggc.iptime.org/book/data/ch2_1.txt")
ch2_1

max(ch2_1)
min(ch2_1)
mean(ch2_1)
median(ch2_1)
summary(ch2_1)

table(ch2_1)
max(table(ch2_1))
table(ch2_1)[table(ch2_1)==max(table(ch2_1))]

Mode(ch2_1)

diff(range(ch2_1))
(dev<-ch2_1-mean(ch2_1))
(devsq<-dev^2)
(variation<-sum(devsq))
(variance<-variation/(length(ch2_1)-1))
var(ch2_1)
sd(ch2_1)

bins<-c(0, 12, 24, 36, 48, 60, 72, 84, 97)
ch2_1
class<-cut(ch2_1, breaks=bins)
class
table(class)
table(class)/length(ch2_1)
transform(table(class), Rel_Freq=prop.table(Freq))

par(mfrow=c(1,2))
hist(ch2_1)
hist(ch2_1, breaks=bins, main="Test Scores", xlab="Score")