Identifying observations that changed from one year to the next

[Stephanie Leigh]

I am not sure how to use dataex on this one, please forgive me. I have data that has individual observations over three school years. For example, each school has 3 separate observations, 1 for the year 17-18, one for 18-19, and one for 20-21. If they are a CEP school CEP = 1 and if not CEP = 0. The number of CEP schools doubled in this time period. I am trying to see if there are similarities in the schools that changed from 0 to 1in this time frame. I can usually find a starting point, but on this one I am stumped. I feel like this should be super simple, but I can't figure this one out. Thank you in advance.

[William Lisowski]

Perhaps this example will start you in a useful direction. With three years and two possible values for CEP each year, there are only 8 possible patterns.

* Example generated by -dataex-. For more info, type help dataex
clear
input float(school year cep)
101 1 0
101 2 0
101 3 0
102 1 1
102 2 0
102 3 0
103 1 0
103 2 1
103 3 0
104 1 1
104 2 1
104 3 0
105 1 0
105 2 0
105 3 1
106 1 1
106 2 0
106 3 1
107 1 0
107 2 1
107 3 1
108 1 1
108 2 1
108 3 1
end
// school changed cep
bysort school (year): egen change = max(cep!=cep[_n-1] & _n>1)
// school went from cep 0 to cep 1
bysort school (year): egen from0to1 = max(cep==1 & cep[_n-1]==0)
// school went from cep 1 to cep 0
bysort school (year): egen from1to0 = max(cep==0 & cep[_n-1]==1)
list, noobs sepby(school)

. list, noobs sepby(school)

  +----------------------------------------------------+
  | school   year   cep   change   from0to1   from1to0 |
  |----------------------------------------------------|
  |    101      1     0        0          0          0 |
  |    101      2     0        0          0          0 |
  |    101      3     0        0          0          0 |
  |----------------------------------------------------|
  |    102      1     1        1          0          1 |
  |    102      2     0        1          0          1 |
  |    102      3     0        1          0          1 |
  |----------------------------------------------------|
  |    103      1     0        1          1          1 |
  |    103      2     1        1          1          1 |
  |    103      3     0        1          1          1 |
  |----------------------------------------------------|
  |    104      1     1        1          0          1 |
  |    104      2     1        1          0          1 |
  |    104      3     0        1          0          1 |
  |----------------------------------------------------|
  |    105      1     0        1          1          0 |
  |    105      2     0        1          1          0 |
  |    105      3     1        1          1          0 |
  |----------------------------------------------------|
  |    106      1     1        1          1          1 |
  |    106      2     0        1          1          1 |
  |    106      3     1        1          1          1 |
  |----------------------------------------------------|
  |    107      1     0        1          1          0 |
  |    107      2     1        1          1          0 |
  |    107      3     1        1          1          0 |
  |----------------------------------------------------|
  |    108      1     1        0          0          0 |
  |    108      2     1        0          0          0 |
  |    108      3     1        0          0          0 |
  +----------------------------------------------------+

[Stephanie Leigh]

Thank you so much!