Stata 如何删除一个月的obs

以下是我的数据示例：

* Example generated by -dataex-. To install: ssc install dataex
clear
input str6 Name double Value long Date
"ABAD1" 1019 18856
"ABAD1" 1149 19430
"ABAD1" 1160 19423
"ABAD1" 1160 19388
"ABAD1" 1220 19380
"ABAD1" 1220 19380
"ABAD1" 1228 19377
"ABAD1" 1228 19377
"ABAD1" 1300 19373
"ABAD1" 1311 19294
"ABAD1" 1311 19252
"ABAD1" 1315 19212
"ABAD1" 1354 19359
"ABAD1" 1360 19357
"ABAD1" 1381 19351
"ABAD1" 1408 19352
"ABAD1" 1394 19191
"ABAD1" 1415 18986
"ABAD1" 1475 19332
"ABAD1" 1512 19030
"ABAD1" 1633 19101
"ABAD1" 1680 19063
"ABAD1" 1771 19128
end
format %tdD_m_Y Date

我想删除每个

Name

值的第一个月观察值

如何做到这一点？

在您使用

dataex

的示例（可读性很强）中，只有一个不同的

名称

，在记录的第一个月只有一个观察值，但这里的代码也适用于多个面板和多个观察值

mofd（）

从每日日期生成每月日期；如果每月日期与专家组第一次观察的每月日期相同，则必须与记录的第一个月相同

* Example generated by -dataex-. To install: ssc install dataex
clear
input str6 Name double Value long Date
"ABAD1" 1019 18856
"ABAD1" 1149 19430
"ABAD1" 1160 19423
"ABAD1" 1160 19388
"ABAD1" 1220 19380
"ABAD1" 1220 19380
"ABAD1" 1228 19377
"ABAD1" 1228 19377
"ABAD1" 1300 19373
"ABAD1" 1311 19294
"ABAD1" 1311 19252
"ABAD1" 1315 19212
"ABAD1" 1354 19359
"ABAD1" 1360 19357
"ABAD1" 1381 19351
"ABAD1" 1408 19352
"ABAD1" 1394 19191
"ABAD1" 1415 18986
"ABAD1" 1475 19332
"ABAD1" 1512 19030
"ABAD1" 1633 19101
"ABAD1" 1680 19063
"ABAD1" 1771 19128
end
format %tdD_m_Y Date

sort Name Date 
list Name Date in 1/5 

     +-------------------+
     |  Name        Date |
     |-------------------|
  1. | ABAD1   17 Aug 11 |
  2. | ABAD1   25 Dec 11 |
  3. | ABAD1   07 Feb 12 |
  4. | ABAD1   11 Mar 12 |
  5. | ABAD1   18 Apr 12 |
     +-------------------+

bysort Name (Date) : drop if mofd(Date) == mofd(Date[1]) 

list Name Date in 1/5 

     +-------------------+
     |  Name        Date |
     |-------------------|
  1. | ABAD1   25 Dec 11 |
  2. | ABAD1   07 Feb 12 |
  3. | ABAD1   11 Mar 12 |
  4. | ABAD1   18 Apr 12 |
  5. | ABAD1   15 May 12 |
     +-------------------+