set.seed(5)

N  = 500
b0 = 3
b1 = .4

s2 = 5
g1 = 1.5
g2 = .015

x        = runif(N, min=0, max=100)
y_homo   = b0 + b1*x + rnorm(N, mean=0, sd=sqrt(s2            ))
y_hetero = b0 + b1*x + rnorm(N, mean=0, sd=sqrt(exp(g1 + g2*x)))

mod.homo   = lm(y_homo~x)
mod.hetero = lm(y_hetero~x)