#
#  MATH 3330 B, October 2001
#
#  Week 5b: Multiple Regression
#


prestige
pairs( prestige )

# simple regression

fit1 <- lm( Income ~ Education , prestige )
summary( fit1 )

# multiple regression

fit2 <- lm( Income ~ Education + Women , prestige)
summary ( fit2 )

# predicting a model over a grid of points

pred <- expand.grid( Education = 6:16, Women = 10*(0:10) ) 
pred
pred$Income2 <- predict(fit2, newdata = pred )
pred$Income1 <- predict(fit1, newdata = pred )
pred

td()		# see in Fun.SSC

wireframe( Income2 ~ Education + Women , pred )
wireframe( Income1 ~ Education + Women , pred )

pred1 <- pred
pred1$Income <- pred$Income1


pred2 <- pred
pred2$Income <- pred$Income2

pred.comb <- stack( pred1, pred2)	# get the 'stack' function from Fun.ssc

wireframe( Income ~ Education + Women | Type., pred.comb)

plot( prestige$Women, prestige$Education )
data.ell( prestige$Women, prestige$Education )		# surprise!