##Topic 8 Exercise##

##load in MPG data set from ggplot2##

library(ggplot2)


#Question 1
#Generate Scatter plot showing the relationship between
#City miles per gallon(cty) and engine displacement(displ)

 plot1<- ggplot(data = mpg, mapping = aes(displ,cty, colour = class))+
  geom_point()+
  #geom_smooth(method=lm, se = F) +
  labs(x = "Engine displacement (liters)", y = "City miles per gallon")+
  theme(text = element_text(size = 10), legend.position = c(.8,.8))



#Question 2
#Generate box plots showing the relationship between
#City miles per gallon(cty) and engine displacement(displ)

plot2 <- ggplot(data = mpg, mapping = aes(displ,cty, colour = class))+
  geom_boxplot()+
  labs(x = "Engine displacement (liters)", y = "City miles per gallon")+
  theme(text = element_text(size = 10), legend.position = c(.8,.8))


#Question 3
#combine the above plots into one plot and 
#save it to a png file with 300 ppi

#load Multiplot script from your saved short course files
source("X://R course (sponsored by BERD) 2021//PartII// Topic8//multiplot.R")


png("Multiplots Q1 Q2.png", width = 5, height = 5, units = "in",res = 300)

multiplot(plot1, plot2, cols = 2)

dev.off()