#========================================================
# R script to read text file containing college GPA data
# into a data frame, extract the males-only data, and
# store the males-only data in a separate text file. The
# input file should have data elements separated on lines
# by spaces, tabs, or commas.
#========================================================
#--------------------------------------------------------
# 1. Designate the working folder where R is to find
# and write the data. User must substitute the appropriate
# directory and file name between the quotes.
#-----------------------------------------------------------
# setwd("c:/myname/myRfolder") # Precede any spaces in
# folder or file names with
# backslash, for example:
# setwd("c:/myname/my\ R\ folder")
#-----------------------------------------------------------
# 2. Read the data in the text file into an R data frame
# named GPA.data. The header=TRUE statement tells R that
# the first line of the text file contains column or variable
# names. The sep=" " option tells R that spaces separate
# data elements in lines of the text file.
#-----------------------------------------------------------
GPA.data=read.table("GPAdata.txt",header=TRUE,sep=" ")
# Use header=FALSE if
# the first line of the
# data file does not
# contain column names.
#-----------------------------------------------------------
# 3. Attach the data frame, making the columns available in R
# as vectors.
#-----------------------------------------------------------
attach(GPA.data)
GPA.data
#-----------------------------------------------------------
# 4. Extract the males-only data from the vectors. (Also
# perform on the data whatever analyses are desired.)
#-----------------------------------------------------------
univGPA.male=univGPA[sex=="m"]
ACT.male=ACT[sex=="m"]
hsGPA.male=hsGPA[sex=="m"]
housing.male=housing[sex=="m"]
#-----------------------------------------------------------
# 5. Gather the males-only vectors into a separate data
# frame.
#-----------------------------------------------------------
GPA.data.male=data.frame(univGPA.male,ACT.male,hsGPA.male,
housing.male)
#-----------------------------------------------------------
# 6. Store the males-only data in a text file in the current
# working folder. Data values in each line will be separated
# by whatever text character designated in the sep=" " argument.
# Print the males-only data in the console just by typing the
# name of the data frame.
#-----------------------------------------------------------
write.table(GPA.data.male,file="GPAdata_male.txt",sep=" ")
GPA.data.male
#-----------------------------------------------------------
# 7. Detach the data frame, removing the vectors from
# workspace, if further analyses with different data are to be
# performed in the R session.
#-----------------------------------------------------------
detach(GPA.data)