SAS中怎么剔除每一類的前面幾行的觀測(cè)值?
比如說(shuō)下表中是一部分?jǐn)?shù)據(jù),實(shí)際上id非常多,起始的年月也不一樣,怎么把每個(gè)id的最初的幾行觀察值去掉?
id DATE year month return marketcap
3457 19860930 1986 9 -0.057143 4148.59375
3457 19861031 1986 10 -0.242424 3911.53125
3457 19861128 1986 11 0.060000 3002.34375
3457 19861231 1986 12 -0.377358 3182.484375
3457 19870130 1987 1 -0.212121 1981.546875
3457 19870227 1987 2 0.000000 1581.53125
3457 19870331 1987 3 -0.384615 1581.53125
3457 19870430 1987 4 -0.062500 973.25
3457 19870529 1987 5 -0.066667 912.421875
3458 19860228 1986 2 0.020408 6033.125
3458 19860331 1986 3 0.025200 6156.25
3458 19860430 1986 4 0.009901 6217.8125
3458 19860530 1986 5 -0.009804 6279.375
3458 19860630 1986 6 -0.013069 6217.8125
3458 19860731 1986 7 -0.010204 6033.125
3458 19860829 1986 8 0.072165 5971.5625
3458 19860930 1986 9 -0.003077 6402.5
3458 19861031 1986 10 0.039216 6317.625
3458 19861128 1986 11 0.056604 6565.375