Graphics for Statistics - figures with ggplot - Chapter 2 - Cleveland Dot plot

Chapter 2 - Dot Charts

Graphics out of the book Graphics for Statistics and Data Analysis with R by Kevin Keen (book home page)

Dot charts of the United Nations budget for 2008-2009

• data:
  

item1<-factor(1:14,
             labels=c("Overall coordination",
               "Political affairs",
               "International law",
               "International cooperation",
               "Regional cooperation",
               "Human rights",
               "Public information",
               "Management",
               "Internal oversight",
               "Administrative",
               "Capital",
               "Safety & security",
               "Development",
               "Staff assessment"))
amount1<-c(718555600,626069600,87269400,398449400,
477145600,259227500,184000500,540204300,35997700,
108470900,58782600,197169300,18651300,461366000)
amount1<-amount1/1000000
df <- data.frame(item1=item1,amount1=amount1)
df

item1  amount1
1       Overall coordination 718.5556
2          Political affairs 626.0696
3          International law  87.2694
4  International cooperation 398.4494
5       Regional cooperation 477.1456
6               Human rights 259.2275
7         Public information 184.0005
8                 Management 540.2043
9         Internal oversight  35.9977
10            Administrative 108.4709
11                   Capital  58.7826
12         Safety & security 197.1693
13               Development  18.6513
14          Staff assessment 461.3660

• now we can build the chart using geom_point() and geom_hline()
  
• first we build a ggplot object and map x to amount1 and y to item1
  
• than we add the point layer (geom_point()) setting the shape to 19 (filled circle)
  
• now we need the horizontal lines, therefore we use geom_hline() and map as.numeric(item1) (which gives 1:14) to yintercept
  

ggplot(df,aes(x=amount1,y=item1)) +
  geom_point(shape=19) +
  geom_hline(aes(yintercept=as.numeric(item1)),linetype=3)
ggsave("fig2_1.png")

• first we reverse the order of the category using reorder() by the negative of the number of the item
  
• then we increase the size of the points a little (size argument in geom_point())
  
• then we change the title of the x-axis and set the limits to c(0,800) (scale_x_continuous())
  
• setting asis.title.y to theme_blank() gets us rid of the title of the y-axis
  
• axis.title.x is managed by theme_text(): we set the text size to 12 and adjust the vertical position (vjust) downwards
  
• last we set the panel background to white using theme_rect() (and because there are some leftovers of the grid lines visible in the frame we set the major grid lines to blank
  

ggplot(df,aes(x=amount1,y=reorder(item1,-as.numeric(item1)))) +
  geom_point(shape=19,size=4) +
  geom_hline(aes(yintercept=as.numeric(item1)),linetype=3) +
  scale_x_continuous("Millions of US Dollars",limits=c(0,800)) +
  opts(axis.title.y=theme_blank(),
       axis.text.y=theme_text(size=12),
       axis.title.x=theme_text(size=12,vjust=-0.7),
       axis.text.x=theme_text(size=12),
       panel.background=theme_rect(fill="white"),
       panel.grid.major=theme_blank())
ggsave("fig2_1b.png")

• remains the ticks of the y-axis, again we must use the hack (as in chapter 1 - have a look there for further information)

png("fig2_1c.png",height=500, width=500)
ggplot(df,aes(x=amount1,y=reorder(item1,-as.numeric(item1)))) +
  geom_point(shape=19,size=4) +
  geom_hline(aes(yintercept=as.numeric(item1)),linetype=3) +
  scale_x_continuous("Millions of US Dollars",limits=c(0,800)) +
  opts(axis.title.y=theme_blank(),
       axis.text.y=theme_text(size=12),
       axis.title.x=theme_text(size=12,vjust=-0.7),
       axis.text.x=theme_text(size=12),
       panel.background=theme_rect(fill="white"),
       panel.grid.major=theme_blank())
g <- grid.gget(gPath("axis-l", "", "", "", "axis.ticks.segments"))
grid.remove(g$name)
dev.off()

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• to change this figure to figure 2.2 we have just to replace geom_hline() by geom_segment() and change therefore some mappings
  

png("fig2_1d.png",height=500, width=500)
ggplot(df,aes(x=amount1,y=reorder(item1,-as.numeric(item1)))) +
  geom_point(shape=19,size=4) +
  geom_segment(aes(yend=reorder(item1,-as.numeric(item1))),xend=0,linetype=3) +
  scale_x_continuous("Millions of US Dollars",limits=c(0,800)) +
  opts(axis.title.y=theme_blank(),
       axis.text.y=theme_text(size=12),
       axis.title.x=theme_text(size=12,vjust=-0.7),
       axis.text.x=theme_text(size=12),
       panel.background=theme_rect(fill="white"),
       panel.grid.major=theme_blank())
g <- grid.gget(gPath("axis-l", "", "", "", "axis.ticks.segments"))
grid.remove(g$name)
dev.off()

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