#
# Epage 137
#
# Written by:
# -- 
# John L. Weatherwax                2009-04-21
# 
# email: wax@alum.mit.edu
# 
# Please send comments and especially bug reports to the
# above email address.
# 
#-----

# version$language == "R" for R version$language == NULL for SPlus

if(is.null(version$language) == FALSE) require(alr3) else library(alr3)

if(is.null(version$language) == FALSE) data(jevons)
attach(jevons)

# a scatterplot matrix
#
plot( Age, Weight ) 

plot( Age, SD )

# we will fit :
#
mwa <- lm( Weight ~ Age, weights = 1 / ( n / SD^2 ) )

delta.method(mwa, "(7.9379 - b0)/b1")