## Author: Elan D. Cohen (edc@stat.cmu.edu)
## Date:   1/22/08
## Goal:   Simulate Galton father/son data (see Freedman, 78)


library(MASS)


## set bivariate normal parameters (from Freedman)
mu.x = 68
mu.y = 69
mu = c(mu.x, mu.y)
sd.x = 2.7
sd.y = 2.7
rho = 0.5
sig.xy = rho*sd.x*sd.y
Sig = matrix(c(sd.x^2, sig.xy, sig.xy, sd.y^2), nrow=2)

n = 1078
X = mvrnorm(n, mu, Sig)
X.lm = lm(X[,2]~X[,1])


## epsilon averaging
eps = 0.5
pt.1 = 64
mean.1 = mean(X[X[,1]>pt.1-eps & X[,1]pt.2-eps & X[,1]