(1978 Automobile Data)
. dataex price mpg in 1/20
----------------------- copy starting from the next line -----------------------
- * Example generated by -dataex-. To install: ssc install dataex
- clear
- input int(price mpg)
- 4099 22
- 4749 17
- 3799 22
- 4816 20
- 7827 15
- 5788 18
- 4453 26
- 5189 20
- 10372 16
- 4082 19
- 11385 14
- 14500 14
- 15906 21
- 3299 29
- 5705 16
- 4504 22
- 5104 22
- 3667 24
- 3955 19
- 3984 30
- end
------------------ copy up to and including the previous line ------------------
像这种有多行的,如何保留 1 4 7 10 ··· 1+3n ··· (即每个3行保留,或者将这些行的观察值提取出来)?
谢谢大神指导。