Agenda

Learn to add legend to a plot using the legend() function. Specifically

position the legend within the plot
modify the layout using ncol and horiz arguments
add title using the title. set of arguments
modify the appearance and position of the legend box
modify the appearance of the text in the legend box

Introduction

Data

users <- readr::read_csv('https://raw.githubusercontent.com/rsquaredacademy/datasets/master/users_device.csv',
  col_types = list(col_date(format = "%m/%d/%y"), col_integer(),
                   col_integer(), col_integer()))

## # A tibble: 33 x 4
##          Date Desktop Mobile Tablet
##        <date>   <int>  <int>  <int>
##  1 2017-10-11    2345    876     92
##  2 2017-10-12    2173    784    111
##  3 2017-10-13    1826    772     97
##  4 2017-10-14    1178   1032    155
##  5 2017-10-15    1239    747    105
##  6 2017-10-16    2158    801     85
##  7 2017-10-17    2682   1307    127
##  8 2017-10-18    2252   1110    112
##  9 2017-10-19    2210    891     93
## 10 2017-10-20    2040    824     94
## # ... with 23 more rows

Data Dictionary

Below is the description of the data set:

Date: date
Desktop: visitors from a desktop device
Mobile: visitors from a mobile device
Tablet: visitors from a tablet device

Line Graph

plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 3000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")

Legend Location

use x and y axis coordinates
use keywords
- top
- bottom
- left
- right
- center
- bottomright
- bottomleft
- topright
- topleft

Legend Location

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'))}

Legend Location

Lines

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'))}

Points

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
points(users$Date, users$Desktop, pch = 2, col = 'blue')
lines(users$Date, users$Mobile, type = "l", col = "red")
points(users$Date, users$Mobile, pch = 2, col = 'red')
lines(users$Date, users$Tablet, type = "l", col = "green")
points(users$Date, users$Tablet, pch = 2, col = 'green')  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), pch = 2)}

Text Placement

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), horiz = TRUE)}

Text Placement

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), ncol = 2)}

Text Placement

Title

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), title = 'Devices', horiz = TRUE)}

Title Color

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), title = 'Devices', title.col = 'red', horiz = TRUE)}

Title Position

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), title = 'Devices', title.adj = 0.1, horiz = TRUE)}

Title Position

Box Appearance

option	argument	values
Box Type	bty	o, n
Background Color	bg	blue, #0000ff
Border Line Type	box.lty	1:5
Border Line Width	box.lwd	0.5, 1, 1.5
Border Line Color	box.col	blue, #0000ff
Horizontal Justification	xjust	0:1
Vertical Justification	yjust	0:1
Text Color	text.col	blue, #0000ff
Text Font	text.font	1:5

Box Type

Background Color

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), title = 'Devices', bg = '#ffff66', horiz = TRUE)}

Border

The following arguments can be used to modify the border of the legend box:

box.lty: line type
box.lwd: line width
box.col: color

Border

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), title = 'Devices', horiz = TRUE,
       box.lty = 3, box.lwd = 1.5, box.col = 'green')}

Justification

The xjust and yjust arguments can be used to position the legend relative to the X and Y axis respectively. Listed below is the value and the respective justification:

0: left justified
0.5: centered
1: right justified

Horizontal Justification

Vertical Justification

Text Appearance

{plot(users$Date, users$Desktop, type = "l", col = "blue", main = 'Daily Visitors',
     ylim = c(0, 4000), xlab = 'Date', ylab = 'Visitors')
lines(users$Date, users$Mobile, type = "l", col = "red")
lines(users$Date, users$Tablet, type = "l", col = "green")  
legend(x = as.Date('2017-10-13'), y = 3900, legend = c('Desktop', 'Mobile', 'Tablet'), lty = 1, 
       col = c('blue', 'red', 'green'), title = 'Devices', 
       text.col = 'green', text.font = 3, horiz = TRUE)}