ustemps=read.table("...\\UStemp.txt",header=TRUE)
attach(ustemps)
ustemps

#to compute the correlation coefficient between temperature and latitude:
cor(temp,lat)
#to draw a scatterplot of the temperature agains latitude:
plot(lat,temp)

#to estimate the simple linear regression line
lm(temp~lat)


#to plot points of several characters on the same graph, use the function "points" as follows:
plot(lat,temp)#--->plots all temps agains latitude
points(lat[1:3],temp[1:3],pch=20,col=2)#--->plots the first three points in the data set in red


#to plot regression line on the graph, use the function abline
#where a is the intercept, and b is the slope
abline(a= 108.728,b=-2.110,col=4)  #draw line in blue