#
# Unit 8 - Data frames 
#
# Sorting a data frame 
#


# Reading a data frame 
setwd("c:/R")
employees <- read.csv("employees.csv")
print(employees)

# one sorting variable 
# What is the sorting order? 
# Note the two indices rows. 
library(dplyr)
sortedDF <- arrange(.data = employees,
                    SALARY)
print(sortedDF)

# original data frame does not change. 
print(employees)

# One variable, descending order. 
# No need to reimport dplyr. 
sortedDF <- arrange(.data = employees,
                    desc(SALARY))
print(sortedDF)



# Two variables: one primary
#                the other secondary 
sortedDF <- arrange(.data = employees,
                    EDUC,
                    desc(SALARY))
print(sortedDF)


sortedDF <- arrange(.data = employees,
                    EDUC,
                    SALARY)
print(sortedDF)