state.x77
newdata=state.x77[,c("Population","Income","Illiteracy","Murder","Frost")]
murder.fit<-lm(Murder~Population+Income+Illiteracy+Frost,data=newdata)

然后报错
Error in model.frame.default(formula = Murder ~ Population + Income +  :   'data'必需是数据框, 不能是矩阵或陣列