可以使用clock函数，计算的差值为毫秒，转换为天数、小时或分钟即可。演示命令如下：

clear
input id str9 (sleep_date sleep_time wake_date wake_time)
1 11jan2019 2154 12jan2019 0716
2 12jan2019 0017 12jan2019 0934
3 12jan2019 0314 12jan2019 0817
4 11jan2019 2354 12jan2019 0730
end

gen double wanted_ms = clock(wake_date + wake_time, "DMY hm") - clock(sleep_date + sleep_time, "DMY hm") 

gen wanted_hr = wanted_ms / (60 * 60 * 1000)

list

结果如下：

     +------------------------------------------------------------------------+
     | id   sleep_d~e   sleep~me   wake_date   wake_t~e   wanted~s   wanted~r |
     |------------------------------------------------------------------------|
  1. |  1   11jan2019       2154   12jan2019       0716   33720000   9.366667 |
  2. |  2   12jan2019       0017   12jan2019       0934   33420000   9.283334 |
  3. |  3   12jan2019       0314   12jan2019       0817   18180000       5.05 |
  4. |  4   11jan2019       2354   12jan2019       0730   27360000        7.6 |
     +------------------------------------------------------------------------+

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