#
x <- c(1.1, 2.2, 3.3, 4.4, 5.5, 6.6)
y <- c(12.21, 14.43, 16.61, 18.83, 21.01, 23.23)

#two notations for plotting
plot(x,y,main="Y versus x -- using x, y")    
plot(y ~ x, main="Y versus X -- using y ~ x") 

correct_fit=lm(y~x)
summary(correct_fit)
abline(correct_fit, col="Red")

wrong_fit=lm(x~y)  #mixing up x and y
summary(wrong_fit)
abline(wrong_fit, col="Blue") #seems like abline doing nothing 

# I can use curve to plot a function 
# this is just a made-up function that is in the plot region
# add=TRUE means add it to existing plot rather than overwrite it
curve(14 + 1.5*x, from=1, to=6, add=TRUE, col="Green")