如何删除一个月的OB [英] How to delete obs for a month

问题描述

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

我要删除每个Name值的第一个月的观测值。

如何执行此操作？

推荐答案

在使用dataex的示例中，记录中只有一个不同的Name和第一个月的一个观察值，但是这里的代码也可以用于多个面板和多个观察值。mofd()从每日日期生成每月日期；如果每月日期与面板中第一个观察的月日期相同，则它必然在记录的第一个月中。

* 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 |
     +-------------------+

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