#----------------------------------------------------------
n=100000; x1 <- rnorm(n, 2, 2) ; x2 <- rnorm(n, 4, 1)
y1 = 2*x1^2 - x2
y2 = x1+ sqrt(abs(x2)) 

hist(y1, nc=200)
hist(y2, nc=200)

plot(x1, x2, cex=0.1)
plot(y1, y2, cex=0.1)

mean(x1)
sd(x1)
mean(x2)
sd(x2)

mean(y1)
sd(y1)
mean(y2)
sd(y2)

z1= x1+x2
z2= x1+x2/2

plot(x2,z3)

#--------------------------------------------------------

ls()
ls

sqrt(3)
sqrt

sqrt <- function(x) "bohh?"
sqrt(3)

base::sqrt(3)
rm(sqrt)

sqrt(3)