x<-c(2,3,4,5,6)
y<-c(4,4,6,6,10)

(sumx<-sum(x))
(sumy<-sum(y))
(mx=mean(x))
(my=mean(y))
(xy<-x*y)
(sumxy<-sum(xy))
(sumxsq<-sum(x^2))
(sumysq<-sum(y^2))

(varx<-(sumxsq-mx*sumx)/4)
(vary<-(sumysq-my*sumy)/4)

(sdx<-sqrt(varx))
(sdy<-sqrt(vary))

(covxy<-(sumxy-mx*sumy)/4)
(corxy<-(covxy/(sdx*sdy)))

(vx<-var(x))
(vy<-var(y))

(sx<-sd(x))
(sy<-sd(y))

(cov(x,y))
(cor(x,y))

nx<-10*x
ny<-10*y

(vnx<-var(nx))
(vny<-var(ny))

(snx<-sd(nx))
(sny<-sd(ny))

(cov(nx,ny))
(cor(nx,ny))