Dear Statalist,

I want to create a variable giving rate of exacerbations per year for each individual identified by the variable id. I have admission dates (variable admissiondate_1 to admissiondate_202) and string variables corresponding to the date variables, denoting ICD_10 codes that are coding for exacerbations (ICD10_1 to ICD10_202). To complicate matters further, I only want the ICD-10 codes starting with J44. Individuals with missing data should be coded as having 0 exacerbations.

Does anyone know how to generate such a variable? I would be highly appreciative for any suggestions!

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float id double(admissiondate_1 admissiondate_2) str21(ICD10_1 ICD10_2)
  1        .        . ""       ""     
  2 20130221        . "M81.9"  ""     
  3        .        . ""       ""     
  4 20160311 20170407 "J44.0"  "M81.9"
  5        .        . ""       ""     
  6        .        . ""       ""     
  7 19991115        . "J45.9"  ""     
  8 19930223 19950515 ""       ""     
  9        .        . ""       ""     
 10 20141005 20141018 "J44.9"  "J22"  
 11 20120618 19950530 "J44.9"  ""     
 12 20001031 20160602 "M81.0"  "M81.9"
 13 20000404        . "J44.9"  ""     
 14 20150413 20150323 "C34.9"  "C34.9"
 15 19990914 19980223 "J44.8"  ""     
 16 20050713 20050902 "J44.9"  "J44.9"
 17 20180428 20180428 "J44.9"  "C34.1"
 18 20100718 19880317 "J44.9"  ""     
 19        .        . ""       ""     
 20        .        . ""       ""     
 21 20011217 20160707 "M81.0"  "J44.9"
 22 19991006 20070803 "J44.9"  "J45.8"
 23 20050415 20070621 "J44.9"  "J44.9"
 24 20110928        . "J45.0"  ""     
 25 20000327 20040406 "J44.9"  "J44.9"
 26 19941019 20010905 ""       "J44.9"
 27 20120917        . "J30.3"  ""     
 28 20030402 20160303 "J44.9"  "J44.9"
 29 20081105 20081118 "C34.9"  "C34.9"
 30 20070601 20081231 "J44.9"  "J44.1"
 31 20060102 20020103 "J44.8"  "J44.9"
 32 19911212 19901101 ""       ""     
 33 20110707 20110911 "C34.9"  "J44.0"
 34 20060425 20050725 "J45.9"  "M81.0"
 35        .        . ""       ""     
 36 19890116 19970912 ""       ""     
 37 20170411 20160819 "C34.9"  "C34.9"
 38 20040625 20041029 "C34.9"  "C34.1"
 39 20110303 20120604 "J44.9"  "J44.9"
 40 20030712 20031121 "J44.1"  "J44.1"
 41 19990928 20010210 "J44.1"  "J44.1"
 42 20080506 20010918 "J45.9"  "J45.9"
 43        .        . ""       ""     
 44 20190906 20120703 "J44.9"  "M81.0"
 45        .        . ""       ""     
 46 20190704 20010621 "J44.9"  "J45.8"
 47 20060508 20060612 "J44.9"  "J44.9"
 48        .        . ""       ""     
 49 19951012 19951221 ""       ""     
 50 20120922 20120708 "J44.9"  "J44.9"
 51 20130124 20000519 "J44.9"  "J30.4"
 52 20030905 20010914 "J44.1"  "J44.9"
 53 19890816        . ""       ""     
 54        .        . ""       ""     
 55 20090217 20110304 "J44.0"  "J44.9"
 56 20190819 20181112 "J45.0"  "J45.0"
 57 20130422 20131115 "J44.9"  "J44.9"
 58 20151204 20150714 "M81.9"  "M81.9"
 59 20160523 20150317 "C34.9"  "C34.9"
 60 19950117 19970304 ""       ""     
 61 20140313 20110706 "J44.9"  "J44.9"
 62 20111111 19960812 "J45.0"  ""     
 63 20070914 20100623 "J45.9"  "J45.9"
 64 20120321 19971124 "M81.0"  ""     
 65 20020208 20050118 "J44.8"  "J44.9"
 66 20050415 20041215 "J44.0"  "J44.0"
 67 20060823 20080222 "J44.9"  "J44.9"
 68 20150430 20150522 "M81.9"  "J44.9"
 69 20120106 20130117 "J44.9"  "J44.0"
 70 20060628 20070815 "J44.9"  "J44.9"
 71 20040428        . "M81.0"  ""     
 72 19931117 20020805 ""       "J44.9"
 73 20160427 20160516 "J44.9"  "J44.1"
 74 20030522 20001010 "J44.9"  "J44.9"
 75 20051114 20060302 "J45.9"  "J45.9"
 76 20051206        . "J31.0"  ""     
 77        .        . ""       ""     
 78 20070221 20170505 "J44.9"  "J44.1"
 79 20120118 20110826 "C34.9"  "J44.9"
 80 20160105 20171227 "J44.9"  "J44.0"
 81 20030410 20040224 "J44.9"  "J20.9"
 82 20070220        . "J22"    ""     
 83 20021028 19980814 "J44.9"  ""     
 84 20040610 20021013 "J44.9"  "J44.9"
 85 20040526 20050615 "J44.9"  "J44.9"
 86 20100929 20190328 "M81.5"  "J44.1"
 87 20191204 19920804 "J45.9"  ""     
 88 19930622 19980828 ""       ""     
 89        .        . ""       ""     
 90        .        . ""       ""     
 91 20101105 20171201 "J45.9"  "M81.9"
 92 20110511 20100927 "C34.9"  "M81.5"
 93        .        . ""       ""     
 94 20090416 20070607 "J42"    "J44.9"
 95 20120918 20111213 "M81.99" "J44.9"
 96 20020122 20030902 "M81.0"  "M81.0"
 97 20090619 20010502 "J44.0"  "J20.9"
 98 20010514 20030401 "J44.0"  "J44.9"
 99 19910822 19920221 ""       ""     
100 20050511 20060124 "M81.0"  "M81.9"
end
Best regards,
Sigrid