前情回顾数据来源清洗数据窗口期为5年：cd C:\Download
u gp_patentinfo, clear
duplicates drop
keep Stkcd year GrantNo ClassNo Type
g id = _n
order id
save ClassNo, replace
*
use ClassNo, clear
qui su y,d
loc min = r(min)
loc max = r(max)
forv i = `min'/`max'{
qui{
use ClassNo, clear
keep if y == `i'
ren C C
split C, p(";")
drop C
gather C*
drop var
drop if v == ""
replace v = substr(v,1,4)
la var v 专利分类号
duplicates drop
compress
}
save ClassNo_split_`i', replace
}
* total
use ClassNo, clear
qui su y,d
loc min = r(min)
loc max = r(max)
forv i = 2000/`max'{
qui{
loc i_1 = `i'-1
loc i_2 = `i'-2
loc i_3 = `i'-3
loc i_4 = `i'-4
loc i_5 = `i'-5
use ClassNo_split_`i_5', clear
ap using ClassNo_split_`i_4', force
ap using ClassNo_split_`i_3', force
ap using ClassNo_split_`i_2', force
ap using ClassNo_split_`i_1', force
keep Stkcd value
duplicates drop
g flag = 0
save temp, replace
*
use ClassNo_split_`i', clear
merge m:1 Stkcd value using temp, nogen keep(1 3)
replac
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