Dear all, I have a question about the command reghdfe(version 6).
What is the difference between the two codes below?
Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input float(lab_size funding) int(year patent_id) long inventor_id float citations byte c double(w1 w2) float age
 4.099 2.93 40  1  7   5.819243 1 3.9895716539976958  4 29
 4.099 2.93 40  1  8   5.819243 1 3.9895716539976958  4 31
 4.099 2.93 40  1 10   5.819243 1 3.9895716539976958  4 55
 4.099 2.93 40  1 12   5.819243 1 3.9895716539976958  4 36
 4.099 2.93 40  1 13   5.819243 1 3.9895716539976958  4 31
 4.099 2.93 40  1 14   5.819243 1 3.9895716539976958  4 45
 4.099 2.93 40  1 15   5.819243 1 3.9895716539976958  4 51
 4.099 2.93 40  1 19   5.819243 1 3.9895716539976958  4 37
 4.749 3.35 40  2  7   5.562209 1  9.495713551788219 10 29
 3.799 2.64 35  3 10   4.793712 1  7.383339990592751  8 50
 3.799 2.64 35  3 13   4.793712 1  7.383339990592751  8 26
 3.799 2.64 35  3 16   4.793712 1  7.383339990592751  8 31
 3.799 2.64 35  3 18   4.793712 1  7.383339990592751  8 25
 3.799 2.64 35  3 20   4.793712 1  7.383339990592751  8 49
 4.816 3.25 40  4  6   5.878152 1  6.771600049640952  7 41
 4.816 3.25 40  4  7   5.878152 1  6.771600049640952  7 29
 4.816 3.25 40  4  8   5.878152 1  6.771600049640952  7 31
 4.816 3.25 40  4 12   5.878152 1  6.771600049640952  7 36
 4.816 3.25 40  4 14   5.878152 1  6.771600049640952  7 45
 4.816 3.25 40  4 18   5.878152 1  6.771600049640952  7 30
 7.827 4.08 43  5  4   4.883052 1  6.387424819273454  7 31
 7.827 4.08 43  5 17   4.883052 1  6.387424819273454  7 60
 5.788 3.67 43  6  3   6.130183 1  7.002765367473977  8 55
 5.788 3.67 43  6  5   6.130183 1  7.002765367473977  8 43
 5.788 3.67 43  6  6   6.130183 1  7.002765367473977  8 44
 5.788 3.67 43  6  7   6.130183 1  7.002765367473977  8 32
 5.788 3.67 43  6 11   6.130183 1  7.002765367473977  8 59
 5.788 3.67 43  6 14   6.130183 1  7.002765367473977  8 48
 5.788 3.67 43  6 16   6.130183 1  7.002765367473977  8 39
 5.788 3.67 43  6 20   6.130183 1  7.002765367473977  8 57
 4.453 2.23 34  7  1   3.470443 1  7.147011498658941  8 26
 4.453 2.23 34  7  2   3.470443 1  7.147011498658941  8 27
 4.453 2.23 34  7  4   3.470443 1  7.147011498658941  8 22
 4.453 2.23 34  7  6   3.470443 1  7.147011498658941  8 35
 4.453 2.23 34  7 11   3.470443 1  7.147011498658941  8 50
 4.453 2.23 34  7 13   3.470443 1  7.147011498658941  8 25
 4.453 2.23 34  7 14   3.470443 1  7.147011498658941  8 39
 4.453 2.23 34  7 15   3.470443 1  7.147011498658941  8 45
 4.453 2.23 34  7 16   3.470443 1  7.147011498658941  8 30
 5.189 3.28 42  8  3   5.726134 1  7.373801426466477  8 54
 5.189 3.28 42  8  6   5.726134 1  7.373801426466477  8 43
 5.189 3.28 42  8  7   5.726134 1  7.373801426466477  8 31
 5.189 3.28 42  8 11   5.726134 1  7.373801426466477  8 58
 5.189 3.28 42  8 14   5.726134 1  7.373801426466477  8 47
 5.189 3.28 42  8 18   5.726134 1  7.373801426466477  8 32
10.372 3.88 43  9  8  1.3354535 1 1.0948582138979546  2 34
 4.082  3.4 42 10  1   6.433572 1  5.936803057894079  6 34
 4.082  3.4 42 10  3   6.433572 1  5.936803057894079  6 54
 4.082  3.4 42 10  7   6.433572 1  5.936803057894079  6 31
 4.082  3.4 42 10 20   6.433572 1  5.936803057894079  6 56
11.385 4.33 44 11  2   2.668204 1 5.9049245321393276  6 37
11.385 4.33 44 11  3   2.668204 1 5.9049245321393276  6 56
11.385 4.33 44 11  8   2.668204 1 5.9049245321393276  6 35
11.385 4.33 44 11 12   2.668204 1 5.9049245321393276  6 40
11.385 4.33 44 11 15   2.668204 1 5.9049245321393276  6 55
11.385 4.33 44 11 17   2.668204 1 5.9049245321393276  6 61
  14.5  3.9 43 12  8  -2.717652 1  9.878314862740554 10 34
  14.5  3.9 43 12 20  -2.717652 1  9.878314862740554 10 57
15.906 4.29 45 13  1 -1.6896555 1  6.543556482804255  7 37
15.906 4.29 45 13 10 -1.6896555 1  6.543556482804255  7 60
15.906 4.29 45 13 12 -1.6896555 1  6.543556482804255  7 41
15.906 4.29 45 13 13 -1.6896555 1  6.543556482804255  7 36
15.906 4.29 45 13 18 -1.6896555 1  6.543556482804255  7 35
 3.299 2.11 34 14  1     3.0559 1  6.525586648816671  7 26
 3.299 2.11 34 14  3     3.0559 1  6.525586648816671  7 46
 3.299 2.11 34 14  6     3.0559 1  6.525586648816671  7 35
 3.299 2.11 34 14  7     3.0559 1  6.525586648816671  7 23
 3.299 2.11 34 14 10     3.0559 1  6.525586648816671  7 49
 3.299 2.11 34 14 14     3.0559 1  6.525586648816671  7 39
 5.705 3.69 43 15  2   5.202066 1   8.68736886042892  9 36
 5.705 3.69 43 15 16   5.202066 1   8.68736886042892  9 39
 4.504 3.18 31 16  1   5.149125 1  .4443091332012228  1 23
 4.504 3.18 31 16 11   5.149125 1  .4443091332012228  1 47
 4.504 3.18 31 16 13   5.149125 1  .4443091332012228  1 22
 4.504 3.18 31 16 17   5.149125 1  .4443091332012228  1 48
 5.104 3.22 41 17  8   4.740935 1  9.224959354351222 10 32
 3.667 2.75 40 18  3   4.795815 1  2.339954775078711  3 52
 3.955 3.43 43 19  1   6.782544 1  2.957500134912027  3 35
 3.955 3.43 43 19 14   6.782544 1  2.957500134912027  3 48
 3.955 3.43 43 19 18   6.782544 1  2.957500134912027  3 33
 3.984 2.12 35 20  3   3.567411 1   6.42041655386527  7 47
 3.984 2.12 35 20 10   3.567411 1   6.42041655386527  7 50
 3.984 2.12 35 20 12   3.567411 1   6.42041655386527  7 31
 3.984 2.12 35 20 14   3.567411 1   6.42041655386527  7 40
 3.984 2.12 35 20 16   3.567411 1   6.42041655386527  7 31
  4.01  3.6 46 21  3    7.30405 1  8.270478884270844  9 58
  4.01  3.6 46 21  9    7.30405 1  8.270478884270844  9 38
  4.01  3.6 46 21 17    7.30405 1  8.270478884270844  9 63
 5.886  3.6 46 22  1   6.796914 1 4.3157892705423615  5 38
 5.886  3.6 46 22  2   6.796914 1 4.3157892705423615  5 39
 5.886  3.6 46 22  4   6.796914 1 4.3157892705423615  5 34
 5.886  3.6 46 22  7   6.796914 1 4.3157892705423615  5 35
 5.886  3.6 46 22  9   6.796914 1 4.3157892705423615  5 38
 5.886  3.6 46 22 10   6.796914 1 4.3157892705423615  5 61
 5.886  3.6 46 22 11   6.796914 1 4.3157892705423615  5 62
 5.886  3.6 46 22 15   6.796914 1 4.3157892705423615  5 57
 5.886  3.6 46 22 17   6.796914 1 4.3157892705423615  5 63
 5.886  3.6 46 22 19   6.796914 1 4.3157892705423615  5 43
 6.342 3.74 46 23  3   4.886721 1  5.145538164492164  6 58
 6.342 3.74 46 23  5   4.886721 1  5.145538164492164  6 46
end


Code:
reghdfe citations funding, a(year inventor_id) group(patent_id) individual(inventor_id)

reghdfe citations funding, a(year inventor_id)


When should I use the group and individual option?What is the model behind the first code which contains group and individual option?

Any help will be appreciated.