# PS6.9 for estimating demand elasticities -- Section 6.11
open data4-4
logs BUSTRAVL FARE GASPRICE INCOME POP DENSITY LANDAREA  
ols l_BUSTRAVL const l_FARE l_GASPRICE l_INCOME l_POP l_DENSITY l_LANDAREA 
omit l_DENSITY 
omit l_GASPRICE  
omit l_FARE