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[Narong Kul]

Hi, I need help with solving this problem of duplicates, drop ,etc.
I have the following data:

I would like to keep the patient with headinj (inc_key A & D) and drop those without (inc_key B & C)
But I also want to keep the remaining body part, duplicates inc_key of A & D
Another word, I want to keep all of the inc_key A & D
How do I write a command for this?
Thank you in advance
Narong

inc_key organ severity headinj
A head 3 yes
A chest 3 .
A abdomen 2 .
B chest 3 .
B abdomen 2 .
C abdomen 2 .
D head 3 yes
D chest 3 ,
D abdomen 2 .

[Carlo Lazzaro]

Narong:
welcome to this forum.
Do you mean something along the following lines?

. bysort inc_key: replace headinj="headpluselse" if headinj[1]=="yes" & headinj=="."


. drop if headinj=="."


. list

     +---------------------------------------------+
     | inc_key     organ   severity        headinj |
     |---------------------------------------------|
  1. |       A      head          3            yes |
  2. |       A     chest          3   headpluselse |
  3. |       A   abdomen          2   headpluselse |
  4. |       D      head          3            yes |
  5. |       D     chest          3   headpluselse |
     |---------------------------------------------|
  6. |       D   abdomen          2   headpluselse |
     +---------------------------------------------+

.

[Bruce Weaver]

Here's another approach that does not depend on the head injury row being listed first for each patient.

* Read in the sample data
clear
input str1 inc_key str15 organ severity str3 headinj
A head 3 yes
A chest 3 .
A abdomen 2 .
B chest 3 .
B abdomen 2 .
C abdomen 2 .
D head 3 yes
D chest 3 ,
D abdomen 2 .
end
* Rename headinj to head
rename headinj head
* Generate a numeric indicator variable for head injury
* so that I can use the egen max() function later
generate byte headinj = head=="yes"
bysort inc_key: egen wanted = max(headinj)
list, sepby(inc_key)
keep if wanted
list, sepby(inc_key)

Output from the final list command:

. list, sepby(inc_key)

     +--------------------------------------------------------+
     | inc_key     organ   severity   head   headinj   wanted |
     |--------------------------------------------------------|
  1. |       A      head          3    yes         1        1 |
  2. |       A     chest          3      .         0        1 |
  3. |       A   abdomen          2      .         0        1 |
     |--------------------------------------------------------|
  4. |       D      head          3    yes         1        1 |
  5. |       D     chest          3      ,         0        1 |
  6. |       D   abdomen          2      .         0        1 |
     +--------------------------------------------------------+

PS- Welcome to the forum Narong Kul, but please take a look at the FAQ for tips on how to write questions in a way that makes it easier for forum members to help you!