# R script to illustrate some summaries of categorical data.

stu.data=read.table("student_survey.txt",header=TRUE)
stu.data
stu.data$gender  # Can use columns of data frame as vectors this
                     #   way if data frame is not attached.

table(stu.data$gender)
barplot(table(stu.data$gender),xlim=c(0,1),width=.1,space=2)

stu.table=table(stu.data$gender,stu.data$political_affiliation)
stu.table
margin.table(stu.table)            # sums counts in the table.
margin.table(stu.table,margin=1)   # margin=1 sums rows.
margin.table(stu.table,margin=2)   # margin=2 sums columns.

barplot(stu.table)
windows()   #  Opens new graphics window; use quartz() for Mac, X11() for Unix.
mosaicplot(stu.table)

stu.mv.data=subset(stu.data,stu.data$gender=="m" & stu.data$vegetarian=="y")
stu.mv.data