code

# Set variable W (salary)
salary <-c(30000, 60000, 30000, 60000, 30000, 60000, 8000, 3000, 10000, 8000, 3000, 10000, 8000, 3000, 10000)

# Set variable X (age)
age <- c(41, 41, 28, 33, 32, 19,41, 28, 33, 32, 19,28, 33, 32, 19)

# Set variable Y (height)
height <- c(182, 172, 160, 182, 182, 172, 160, 178, 181, 172, 160, 178, 181, 178, 181)

# Set variable Z (occupation)
occupation <- c('Doctor', 'Police', 'Teacher', 'Teacher', 'Police','Doctor', 'Police', 'Teacher', 'Teacher', 'Police','Doctor', 'Police', 'Teacher', 'Teacher', 'Police')

# Create DataFrame
df <- data.frame(salary, age, height, occupation)

# Show DataFrame
print (df)

# load lattice package
require(lattice)

# drop doctor to show only two plots
dropData <- droplevels(subset(df, occupation != "Doctor"))
print(xyplot(salary~age | occupation, data = dropData, grid = TRUE, main = "A Simple Plot for the GCI"))