Multi Variable Visualization

library(ggplot2)
?mpg
head(mpg)
str(mpg)

# Identify a scatter point
attach(mtcars)
plot(mpg, wt) 
identify(x = mpg, y = wt, n = 3, label = row.names(mtcars))
detach(mtcars)

# Two Variables Viz
ggplot(mpg, aes(class, hwy)) + geom_point()
ggplot(mpg, aes(class, hwy)) + geom_jitter()
ggplot(mpg, aes(reorder(class, hwy), hwy)) + geom_point()

ggplot(mpg, aes(displ, hwy)) + geom_point()

# Three Variables Viz - Color (Cat., Cont.)
ggplot(mpg, aes(displ, hwy, colour = class)) + geom_point()
ggplot(mpg, aes(displ, hwy, colour = cyl)) + geom_point()

# Three Variables Viz - Size (Cat, Cont.)
ggplot(mpg, aes(displ, hwy, size = drv)) + geom_point()
ggplot(mpg, aes(displ, hwy, size = cyl)) + geom_point()

# Three Variables Viz - Shape (Cat)
ggplot(mpg, aes(displ, hwy, shape = drv)) + geom_point()

# Four Variables Viz - Combine Color, Shape & Size
ggplot(mpg, aes(displ, hwy, color = class, shape = drv)) + geom_point()
ggplot(mpg, aes(displ, hwy, color = class, size = drv)) + geom_point()

# Four - Six  Variable Viz - Facetting + Color, Shape, Size
ggplot(mpg, aes(displ, hwy, color = class)) + geom_point() + facet_wrap(~ cyl)
ggplot(mpg, aes(displ, hwy, color = class)) + geom_point() + facet_grid(~ cyl)
ggplot(mpg, aes(displ, hwy)) + geom_point() + facet_grid(drv ~ cyl)
ggplot(mpg, aes(displ, hwy, color = class)) + geom_point() + facet_grid(drv ~ cyl)
ggplot(mpg, aes(displ, hwy, color = class, size = trans)) + 
  geom_point() + facet_grid(drv ~ cyl)
ggplot(mpg, aes(displ, hwy, color = class, size = trans)) + 
  geom_point(alpha = 0.4) + facet_grid(drv ~ cyl)

# More than Three - Matrices (SPLOM, GGally)
plot(mpg)
plot(iris)
library(GGally)
mpg_select <- subset(mpg, select = c(displ, hwy, drv))
plot(mpg_select)
ggpairs(mpg_select)
ggpairs(mpg_select, diag = list(continuous = "bar", discrete = "bar"),
        axisLabels = 'show')
ggpairs(mpg_select, diag = list(continuous = "bar", discrete = "bar"),
        upper = list(continuous = "density", combo = "dot"),
        axisLabels = 'show')

# More than Three - Parallel Coordinates
ggparcoord(mpg, column = c(1:11), groupColumn = 4)