Hello all,

I am working a matched case-control study (matched on age and sex). In the below example data set, "case_id" is ID for cases and "control_id" is ID of controls for their respective cases. I would like to add a new row for each case in each group so that I can identify case and controls in each group for further calculations. Please kindly suggest me how I can do it. I am using Stata 16.1.

The example data set and the desired data (in table) are as below;

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input long case_id str4 birth_yr str1 sex long control_id byte drawing
 2 "1939" "2"  376946 1
 2 "1939" "2" 2942780 2
 2 "1939" "2"   47779 3
 3 "1988" "2" 3315976 5
 3 "1988" "2" 1046611 1
 3 "1988" "2" 2263204 4
 3 "1988" "2"  174519 3
 3 "1988" "2" 2698292 2
 5 "1933" "1"  570729 2
 5 "1933" "1" 1473493 1
 5 "1933" "1" 1713036 3
18 "1948" "1" 2549094 5
18 "1948" "1"  445970 2
18 "1948" "1"  893367 1
18 "1948" "1" 2310288 3
18 "1948" "1"  766227 4
21 "1920" "2" 2136179 1
21 "1920" "2" 3706241 3
21 "1920" "2"  400520 2
27 "1938" "1" 1278141 2
27 "1938" "1" 3137797 1
35 "1943" "1" 3689694 1
35 "1943" "1" 3049360 3
35 "1943" "1" 1701121 2
37 "1982" "2" 2254857 3
37 "1982" "2" 3657569 4
37 "1982" "2" 1137049 1
37 "1982" "2"   20248 5
37 "1982" "2" 3312689 2
41 "1931" "1" 2936236 2
41 "1931" "1" 1279751 1
42 "1918" "1" 3884722 1
42 "1918" "1"  710923 4
42 "1918" "1" 3143734 2
42 "1918" "1"  217435 3
42 "1918" "1" 1925103 5
44 "1944" "1"  263386 2
44 "1944" "1" 3640281 1
44 "1944" "1" 4024601 5
44 "1944" "1" 3604175 4
44 "1944" "1" 4027191 3
45 "1989" "1" 2548475 4
45 "1989" "1" 1730091 5
45 "1989" "1" 2545426 3
45 "1989" "1" 1716034 2
45 "1989" "1" 2536701 1
47 "1977" "2"  916222 4
47 "1977" "2" 2907055 2
47 "1977" "2"  803776 1
47 "1977" "2" 3945266 5
47 "1977" "2" 1722669 3
59 "1925" "2" 2757129 3
59 "1925" "2"   43313 1
59 "1925" "2" 2515262 2
59 "1925" "2" 3803170 4
60 "1944" "2" 3864710 2
60 "1944" "2" 1587805 1
60 "1944" "2" 3314789 3
60 "1944" "2" 1598217 4
69 "1953" "2" 2615813 5
69 "1953" "2" 1368929 2
69 "1953" "2"  519307 3
69 "1953" "2" 1302334 1
69 "1953" "2" 2876821 4
72 "1934" "2" 2881280 2
72 "1934" "2" 2290634 1
72 "1934" "2"  388080 3
74 "1929" "1" 3710540 1
74 "1929" "1" 2914260 2
75 "1987" "2"  428090 3
75 "1987" "2" 1797948 2
75 "1987" "2" 1196924 1
75 "1987" "2" 1554935 4
75 "1987" "2" 2819514 5
79 "1961" "2" 1790102 3
79 "1961" "2" 3069242 2
79 "1961" "2"   80233 1
79 "1961" "2" 2920718 4
79 "1961" "2"  654452 5
82 "1940" "1"  786277 2
82 "1940" "1"   84262 1
83 "1946" "1" 1728796 5
83 "1946" "1" 2562225 3
83 "1946" "1" 2923787 1
83 "1946" "1"  396347 2
83 "1946" "1" 3636393 4
85 "1973" "2" 3597618 4
85 "1973" "2" 3059310 5
85 "1973" "2"  312933 3
85 "1973" "2"  765396 1
85 "1973" "2"  727242 2
87 "1986" "2" 1235065 5
87 "1986" "2" 3885966 2
87 "1986" "2"  323953 4
87 "1986" "2"   33525 1
87 "1986" "2"   37721 3
88 "1924" "1" 3543505 2
88 "1924" "1" 3276827 1
89 "1932" "2"  296052 2
89 "1932" "2"  696841 1
end

The desired data
case_id birth_yr sex control_id drawing
2 1939 2 2 0
2 1939 2 376946 1
2 1939 2 2942780 2
2 1939 2 47779 3
Best Regards,
Moon Lu