如何查找组内观察是否具有特定值
How to find if observation within group has certain values
说我有这个MWE：
clear all
input str2 person enr_year enr_term
"a" 2000 1
"a" 2000 2
"a" 2000 2
"a" 2000 3
"a" 2000 3
"a" 2001 1
"a" 2001 2
"a" 2001 3
"a" 2002 2
"a" 2002 2
"a" 2003 2
"a" 2006 1
"a" 2006 2
"a" 2008 2
"b" 2000 2
"b" 2001 3
end
label define term 1 "Summer" 2 "Fall" 3 "Spring"
label values enr_term term
一些解释是为了。这是学校招生数据。 person是一个人，凡事都要在人之内完成。
enr_year 是一个学年。 enr_term 是一个学术术语。夏季和秋季在Spring之前的原因是因为这一年是学年，而不是日历年。
数据中的每一行都隐含地表示在给定年份和学期注册的人。
我的任务是创建两个指标变量：enr_this_spring 和 enr_next_fall。我可以成功获得enr_this_spring。我已经包含了这样做的代码，以防逻辑有助于弄清楚如何获得 enr_next_fall。
*这些指标变量应该只为秋季入学的观察结果创建。
enr_this_spring表示此人报名了以下spring。因为我们只为秋季学期制作这个变量，所以如果同一年有 spring 观察，这将为 1。否则它将为 0，即使下一年有 spring 观察。
如果下一年有秋季观测，enr_next_fall 将为 1。如下所述，如果学生在 x 的秋季入学，而不是在 x+1 的秋季入学，而是在 x+n 的秋季入学，那么我不确定如何克服的问题就会出现，
其中 n>1。
如果同一年内有两次秋季观察（多个入学时期，可能学生同时被两所学校录取），它们将取相同的值。
这是我想要得到的：
clear all
input str2 person enr_year enr_term enr_this_spring enr_next_fall
"a" 2000 1 . . // missing because not Fall
"a" 2000 2 1 1 // 1 b/c a/2000/3; 1 b/c a/2001/2
"a" 2000 2 1 1 // same reasons as line directly above
"a" 2000 3 . . // missing because not Fall
"a" 2000 3 . . // missing because not Fall
"a" 2001 1 . . // missing because not Fall
"a" 2001 2 1 1 // 1 b/c a/2001/3; 1 b/c a/2002/2
"a" 2001 3 . . // missing because not Fall
"a" 2002 2 0 1 // 0 b/c no a/2002/3; 1 b/c a/2003/2
"a" 2002 2 0 1 // same reasons as line directly above
"a" 2003 2 0 0 // 0 b/c no a/2003/2; 0 b/c no a/2004/2
"a" 2006 1 . . // missing because not Fall
"a" 2006 2 0 0 // 0 b/c no a/2006/3; 0 b/c no a/2007/2
"a" 2008 2 0 0 // 0 b/c no a/2008/3; 0 b/c no a/2009/2
"b" 2000 2 0 0 // 0 b/c no a/2000/3; 0 b/c no a/2001/2
"b" 2001 3 . . // missing because not Fall
end
label define term 1 "Summer" 2 "Fall" 3 "Spring"
label values enr_term term
从原始数据入手，我首先可以成功得到enr_this_spring如下：
*Create indicators for if the term is spring and if term is fall
gen is_spring = enr_term == 3
gen is_fall = enr_term ==2
*Get the maximum value, within person and year
bys person enr_year: egen enr_this_spring = max(is_spring)
replace enr_this_spring=. if is_fall!=1
我不确定如何创建一个指标来判断此人是否在明年秋季入学。
这是我尝试过的方法，并解释了为什么它按照代码不起作用：
*Preserve the data. We are going to process it and merge back on
preserve
*We only are concerned about fall attendance for this part
keep if enr_term==2
*We only want one observation per term, as duplicates mess up the code
bys person enr_year enr_term: keep if _n==1
*Make a variable that is a constant 1
gen one = 1
*Make a variable, enr_next_fall that is 1 if the person enrolled in the fall
* in the following observation. Note that we do this within group and sort
* by enr_year
bys person (enr_year): gen enr_next_fall = one[_n+1]
* Replace missing with 0. This only affects the final observation within group
replace enr_next_fall = 0 if missing(enr_next_fall)
*Create temporary file, to be merged on
tempfile a
save `a'
restore
*Merge on the temporary file
merge m:1 person enr_year enr_term using `a'
drop is_spring is_fall one _merge
如果此人没有在第二年秋季注册但又回来了，这并不能满足我的要求。也许他们生病了，错过了整个学年。我应该如何解决这个问题？
我想我已经弄明白了：
clear all
input str2 person enr_year enr_term
"a" 2000 1
"a" 2000 2
"a" 2000 2
"a" 2000 3
"a" 2000 3
"a" 2001 1
"a" 2001 2
"a" 2001 3
"a" 2002 2
"a" 2002 2
"a" 2003 2
"a" 2006 1
"a" 2006 2
"a" 2008 2
"b" 2000 2
"b" 2001 3
end
label define term 1 "Summer" 2 "Fall" 3 "Spring"
label values enr_term term
*Create indicators for if the term is spring and if term is fall
gen is_spring = enr_term == 3
gen is_fall = enr_term ==2
*Get the maximum value, within person and year
bys person enr_year: egen enr_this_spring = max(is_spring)
replace enr_this_spring=. if is_fall!=1
*Create enr_next_fall variable. Merge back on
preserve
keep if enr_term==2
bys person enr_year: keep if _n==1
bys person (enr_year): gen next = enr_year[_n+1]
replace next = next - 1
gen enr_next_fall = enr_year==next
drop next
tempfile fall
save `fall'
restore
merge m:1 person enr_year using `fall'
drop _merge
replace enr_next_fall = . if enr_term!=2
说我有这个MWE：
clear all
input str2 person enr_year enr_term
"a" 2000 1
"a" 2000 2
"a" 2000 2
"a" 2000 3
"a" 2000 3
"a" 2001 1
"a" 2001 2
"a" 2001 3
"a" 2002 2
"a" 2002 2
"a" 2003 2
"a" 2006 1
"a" 2006 2
"a" 2008 2
"b" 2000 2
"b" 2001 3
end
label define term 1 "Summer" 2 "Fall" 3 "Spring"
label values enr_term term
一些解释是为了。这是学校招生数据。 person是一个人，凡事都要在人之内完成。
enr_year 是一个学年。 enr_term 是一个学术术语。夏季和秋季在Spring之前的原因是因为这一年是学年，而不是日历年。
数据中的每一行都隐含地表示在给定年份和学期注册的人。
我的任务是创建两个指标变量：enr_this_spring 和 enr_next_fall。我可以成功获得enr_this_spring。我已经包含了这样做的代码，以防逻辑有助于弄清楚如何获得 enr_next_fall。
*这些指标变量应该只为秋季入学的观察结果创建。
enr_this_spring表示此人报名了以下spring。因为我们只为秋季学期制作这个变量，所以如果同一年有 spring 观察，这将为 1。否则它将为 0，即使下一年有 spring 观察。
enr_next_fall 将为 1。如下所述，如果学生在 x 的秋季入学，而不是在 x+1 的秋季入学，而是在 x+n 的秋季入学，那么我不确定如何克服的问题就会出现，
其中 n>1。
如果同一年内有两次秋季观察（多个入学时期，可能学生同时被两所学校录取），它们将取相同的值。
这是我想要得到的：
clear all
input str2 person enr_year enr_term enr_this_spring enr_next_fall
"a" 2000 1 . . // missing because not Fall
"a" 2000 2 1 1 // 1 b/c a/2000/3; 1 b/c a/2001/2
"a" 2000 2 1 1 // same reasons as line directly above
"a" 2000 3 . . // missing because not Fall
"a" 2000 3 . . // missing because not Fall
"a" 2001 1 . . // missing because not Fall
"a" 2001 2 1 1 // 1 b/c a/2001/3; 1 b/c a/2002/2
"a" 2001 3 . . // missing because not Fall
"a" 2002 2 0 1 // 0 b/c no a/2002/3; 1 b/c a/2003/2
"a" 2002 2 0 1 // same reasons as line directly above
"a" 2003 2 0 0 // 0 b/c no a/2003/2; 0 b/c no a/2004/2
"a" 2006 1 . . // missing because not Fall
"a" 2006 2 0 0 // 0 b/c no a/2006/3; 0 b/c no a/2007/2
"a" 2008 2 0 0 // 0 b/c no a/2008/3; 0 b/c no a/2009/2
"b" 2000 2 0 0 // 0 b/c no a/2000/3; 0 b/c no a/2001/2
"b" 2001 3 . . // missing because not Fall
end
label define term 1 "Summer" 2 "Fall" 3 "Spring"
label values enr_term term
从原始数据入手，我首先可以成功得到enr_this_spring如下：
*Create indicators for if the term is spring and if term is fall
gen is_spring = enr_term == 3
gen is_fall = enr_term ==2
*Get the maximum value, within person and year
bys person enr_year: egen enr_this_spring = max(is_spring)
replace enr_this_spring=. if is_fall!=1
我不确定如何创建一个指标来判断此人是否在明年秋季入学。
这是我尝试过的方法，并解释了为什么它按照代码不起作用：
*Preserve the data. We are going to process it and merge back on
preserve
*We only are concerned about fall attendance for this part
keep if enr_term==2
*We only want one observation per term, as duplicates mess up the code
bys person enr_year enr_term: keep if _n==1
*Make a variable that is a constant 1
gen one = 1
*Make a variable, enr_next_fall that is 1 if the person enrolled in the fall
* in the following observation. Note that we do this within group and sort
* by enr_year
bys person (enr_year): gen enr_next_fall = one[_n+1]
* Replace missing with 0. This only affects the final observation within group
replace enr_next_fall = 0 if missing(enr_next_fall)
*Create temporary file, to be merged on
tempfile a
save `a'
restore
*Merge on the temporary file
merge m:1 person enr_year enr_term using `a'
drop is_spring is_fall one _merge
如果此人没有在第二年秋季注册但又回来了，这并不能满足我的要求。也许他们生病了，错过了整个学年。我应该如何解决这个问题？
我想我已经弄明白了：
clear all
input str2 person enr_year enr_term
"a" 2000 1
"a" 2000 2
"a" 2000 2
"a" 2000 3
"a" 2000 3
"a" 2001 1
"a" 2001 2
"a" 2001 3
"a" 2002 2
"a" 2002 2
"a" 2003 2
"a" 2006 1
"a" 2006 2
"a" 2008 2
"b" 2000 2
"b" 2001 3
end
label define term 1 "Summer" 2 "Fall" 3 "Spring"
label values enr_term term
*Create indicators for if the term is spring and if term is fall
gen is_spring = enr_term == 3
gen is_fall = enr_term ==2
*Get the maximum value, within person and year
bys person enr_year: egen enr_this_spring = max(is_spring)
replace enr_this_spring=. if is_fall!=1
*Create enr_next_fall variable. Merge back on
preserve
keep if enr_term==2
bys person enr_year: keep if _n==1
bys person (enr_year): gen next = enr_year[_n+1]
replace next = next - 1
gen enr_next_fall = enr_year==next
drop next
tempfile fall
save `fall'
restore
merge m:1 person enr_year using `fall'
drop _merge
replace enr_next_fall = . if enr_term!=2