# sortMajors.R
#
# (c) 2007 by Mary E. Beckman for Linguistics H286
#
# Script using the file majors.txt that shows how to do various 
# things that would be useful for gathering the primary data and 
# making the histograms for Data Analysis Problem 1 on "Counting 
# words of different lengths"

# Any line that has a hashmark (#) at the beginning is a comment. 
# Most of these are explanations of the R code in the neighboring 
# lines.  A good strategy is to read the comments around the R 
# code and then experiment with running different parts of the 
# code, to see what each part does.  For example ....

###
# Start by setting the working directory to the folder where you 
# have stored the file majors.txt that we made in class on Wednesday
# September 26.  On Mary's laptop this folder is on the C: drive in 
# a folder called Lx286, so she would use the following command:
setwd('c:/Lx286')

# The syntax of this line is the simplest possible.  It uses the 
# command setwd() using the argument 'c:/Lx286' to name the "path"  
# to the folder.

###
# Next read the file majors.txt and assign the contents to a 
# variable called "majors" using this next command.  
majors=read.table("majors.txt")

# This command has two parts.  The part to the right of the 
# assignment operator (=) uses the command read.table() with the 
# argument "majors.txt", which is the name of the file to be read 
# in as a table.  The part to the left of the assignment operator 
# specifies the name of the variable which then stands in for the 
# table that you read in.  Try running just this part:
read.table("majors.txt")
# to compare the effects of running the command without assigning 
# the results to anything.  Also, no try typing just:
majors
# to see what you did in the first command.  

###
# Use the following command to see how big the table is.
dim(majors)

# You should get something that looks like this on your R console:
# [1] 27  1
# This tells you that the table majors has 27 rows and 1 column. 

# You can assign a name to the column using the names() command:
names(majors)="major"

# You can now refer to the column either by its number, like this:
majors[,1]

# or by its name, like this:
majors[,"major"]

# And you can refer to rows similarly, using the number(s) of the 
# row(s), like this (for the first 3 rows):
majors[1:3,]

# You should get something that looks like this on your R console:
# [1] performance               vocalmusiceducation      
# [3] instrumentalmusiceduction
# 14 Levels: anthropology Arabic Chinese German ... vocalmusiceducation

###
# This next command sorts the column.
sort(majors[,1])

# You can also overwrite the original column, by assigning the 
# sorted values to it, like this:
majors[,1]=sort(majors[,1])

# This makes it easier to count the tokens of each type.

# You can figure out what the different types are by asking 
# what "levels" the variable has, like this:
levels(majors[,"major"])

# This next command counts the tokens of the different types:
summary(majors[,"major"])

# You can assign the result of that command to a new variable 
# called majorTypes like this:
majorTypes=summary(majors[,"major"])

# or if you prefer to have them in sorted order, like this:
majorTypes=sort(summary(majors[,"major"]))

# And then you can make a bar plot, like this:
barplot(majorTypes)