#
# Unit 7 - Data frames 
#
# Column names and row labels 
#

# Column names

# Getting column names
id <- c(1, 2, 3, 4)
gender <- c(2, 2, 1, 2)
educ <- c(12, 12, 15, 10)
salary <- c(11912.44, 10753.82, 5113.94, 8883.05)
employees <- data.frame(id, gender, educ, salary)
print(employees)

print(names(employees))
print(class(names(employees)))
print(colnames(employees))

setwd("c:/R")
employees <- read.csv("employees.csv")
print(employees)
print(names(employees)) 


# Setting names while producing a data frame

# data.frame() 
# also applies to cbind() 
employees <- data.frame(id, SEX = gender, YEARS = educ, INCOME = salary)
print(employees)
print(names(employees))


# Changing names after producing a data frame
employees <- read.csv("employees.csv")
print(names(employees))
names(employees) <- c("ID","FNAME", "LNAME", "SEX", "YEARS","INCOME")
print(employees)
print(names(employees))



# Note - a change in data.frame whose 
# source is in a data file does not change 
# the data file. 
employees <- read.csv("employees.csv")
print(employees)


# Back to chaning names 
# Any guess about the result of 
# This attempt to change the 
# one column's name? 
employees <- read.csv("employees.csv")
print(names(employees))
names(employees) <- c("EDUC")
print(employees)
print(names(employees))



# Changing names: with dplyr's rename() 

# We must first import the required library. 
library(dplyr)

# producing a new data frame with 
# different name(s)
employees <- read.csv("employees.csv")
print(names(employees))
newEmployees <- rename (.data = employees, YEARS = EDUC)
print(newEmployees)
print(names(newEmployees))


# The column names in the original 
# data frame are not changed. 
print(names(employees))


# Changing more than one name 
employees <- read.csv("employees.csv")
newEmployees <- rename (.data = employees, 
                        SEX = GENDER,
                        YEARS = EDUC)
print(names(newEmployees))


# Row labels 

# Getting them
employees <- read.csv("employees.csv")
print(employees)
print(rownames(employees))

print(class(rownames(employees))) 

# changing them 
print(letters)

rownames(employees) <- letters[1:10]
print(employees)
print(rownames(employees))