'/ Oil curse table 5.1 You need install package dplyr/ ' library(dplyr) t.test(x$dom_conflict_onset_2[x$oil_gas_value100==0],x$dom_conflict_onset_2[x$oil_gas_value100==1],alternative="less") tdl<-filter(x,gdpcap2000_sup<5000) tdh<-filter(x,gdpcap2000_sup>4999) t.test(tdh$dom_conflict_onset_2[tdh$oil_gas_value100==0],tdh$dom_conflict_onset_2[tdh$oil_gas_value100==1],alternative="less") t.test(tdl$dom_conflict_onset_2[tdl$oil_gas_value100==0],tdl$dom_conflict_onset_2[tdl$oil_gas_value100==1],alternative="less") tdb89<-filter(x,year<1990) tda89<-filter(x,year>1989) t.test(tdb89$dom_conflict_onset_2[tdb89$oil_gas_value100==0],tdb89$dom_conflict_onset_2[tdb89$oil_gas_value100==1],alternative="less") t.test(tda89$dom_conflict_onset_2[tda89$oil_gas_value100==0],tda89$dom_conflict_onset_2[tda89$oil_gas_value100==1],alternative="less")