本文介绍了识别类别变量的唯一级别的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个身份证号码清单，以及他们在特定日期获得的药品类型。
I have a list of person ids, and the types of medicines they got on specific dates.
我想创建一个变量 c的信息，以便显示可以直接复制和粘贴的数据示例。您需要一些工程使其易于使用。
Please find out about dataex from SSC to be able to show data examples that can be copied and pasted directly. Yours required some engineering to be made easy to use.
您的问题已经是Stata常见问题解答。在发布前仔细阅读常见问题是一个好主意。
Your problem is already a Stata FAQ found here. It is a good idea to look through the FAQs before posting.
* Example generated by -dataex-. To install: ssc install dataex clear input float p_id str8 agent_type float(wanted date) 1001 "thiazide" 1 15322 1001 "thiazide" 1 15442 1001 "thiazide" 1 15536 1001 "arb" 2 15580 1001 "CCB" 3 15609 1001 "arb" 2 15609 1001 "CCB" 3 15623 1001 "thiazide" 1 15623 1001 "arb" 2 15623 1001 "CCB" 3 15684 1001 "arb" 2 15684 2001 "ace_inhi" 1 14433 2001 "ace_inhi" 1 14458 2001 "ace_inhi" 1 14481 2001 "ace_inhi" 1 14539 2001 "CCB" 2 14566 2001 "ace_inhi" 1 14566 2001 "CCB" 2 14592 2001 "CCB" 2 14621 2001 "CCB" 2 14643 2001 "arb" 3 14643 2001 "CCB" 2 14671 end format date %td bysort p_id agent_type (date) : gen firstdate = date[1] egen group = group(p_id firstdate agent_type) bysort p_id (group date agent_type): gen count = sum(group != group[_n-1]) assert count == wanted
请注意，该代码考虑了在同一天首次使用两种或多种药物的可能性，同一个人。
Note that the code takes care of the possibility that two or more drugs are first used on the same day by the same person.
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