Using Line Segments to Compare Values in R

customlegend.R

library(RColorBrewer)
colors = brewer.pal(8, "Dark2")

library(ggplot2)

data <- as.data.frame(USPersonalExpenditure) # data from package datasets
data$Category <- as.character(rownames(USPersonalExpenditure)) # this makes things simpler later

ggplot(data,
  aes(x = Expenditure,
    y = Category)) +
labs(x = "Expenditure",
  y = "Category") +
geom_segment(aes(x = data$"1940",
    y = Category,
    xend = data$"1960",
    yend = Category),
  size = 1) +
geom_point(aes(x = data$"1940",
    color = "1940"), # these can be any string, they just need to be unique identifiers
  size = 4, 
  shape = 15) +
geom_point(aes(x = data$"1960",
    color = "1960"),
  size = 4, 
  shape = 15) +
theme(legend.position = "bottom") +
scale_color_manual(name = "Year", # or name = element_blank()
  labels = c(1940, 1960),
  values = colors)

segments.R

library(ggplot2)

data <- as.data.frame(USPersonalExpenditure) # data from package datasets
data$Category <- as.character(rownames(USPersonalExpenditure)) # this makes things simpler later

ggplot(data,
	aes(x = Expenditure,
		y = Category)) +
labs(x = "Expenditure",
	y = "Category") +
geom_segment(aes(x = data$"1940",
		y = Category,
		xend = data$"1960",
		yend = Category),
	size = 1) +
geom_point(aes(x = data$"1940",
	color = "1940"),
	size = 4, shape = 15) +
geom_point(aes(x = data$"1960",
	color = "1960"),
	size = 4, shape = 15) +
scale_color_discrete(name = "Year") +
theme(legend.position = "bottom")