data lead; input year month gas blood water air furn floor window ; cards; 1979 9 . 7.3 3 . . . . 1979 10 . 7 9.5 . . . . 1979 11 . 6.6 1.4 . . . . 1979 12 . 6.9 4.5 . . . . 1980 1 . 6.6 1.6 . . . . 1980 2 . 5.6 3 . . . . 1980 3 141 6.4 5.5 .12 4.5 5.8 38 1980 4 166 6.1 5 .15 6.5 6.5 24 1980 5 161 5.7 6.7 .18 9.3 10.7 30 1980 6 170 6.9 3.2 .09 3.6 5.4 70 1980 7 148 7 4 .16 14.5 35.6 105 1980 8 136 7.2 5.1 .22 18.1 31.7 62 1980 9 169 6.6 6 .16 16 25 87 1980 10 109 5.7 3.4 .15 13.8 17.3 72 1980 11 117 5.7 3 .07 5.2 65.7 172 1980 12 87 5.3 2.1 .05 7.5 5.3 106 1981 1 105 4.9 6.8 .08 7.6 11.8 30 1981 2 73 5.4 8.1 .01 8.5 9.2 28 1981 3 82 4.5 3.6 .02 1.4 2.3 14 1981 4 75 6 4.3 .09 1.6 2.8 20 ; run;