* do-file for Supplementary Exercises 2.12, 2.27, 2.28 and 2.60 of IPS7e
version 15 /* works also with versions 13-14 */

import delimited "R:\Chapter 2\ex02_012.csv"
scatter fuel speed
pwcorr speed fuel, sig

generate speed_mph=speed/1.609
generate fuel_gpm=fuel*(1.609/3.785)
scatter fuel_gpm speed_mph
pwcorr fuel_gpm speed_mph, sig

generate milespergallon=1/fuel_gpm
scatter milespergallon speed
pwcorr speed milespergallon, sig

* 2.60: regression model
regress fuel speed
twoway (scatter fuel speed) (lfit fuel speed)
predict resid, res
total(resid)
scatter resid speed