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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Need help with combing observations by using by: command along with subscripting |

Date |
Wed, 6 Feb 2013 18:26:27 +0000 |

The context is apparently that observations for each distinct person occur in pairs. If so, this is a general trick: bysort PATIENTno : replace whatever = whatever[3 - _n] if missing(whatever) If that looks a bit odd, let us just run through the possibilities. If whatever[1] is missing, you want to copy whatever[2]. (If whatever[2] is missing too, no harm done.) If whatever[2] is missing, you want to copy whatever[1]. (If whatever[1] is missing too, no harm done.) -whatever- can be numeric or string: same code applies. The rule [3 - _n] ties these cases together. If _n is 1 then 3 - _n is 2 and vice versa. If it looked odd a few lines ago, it now seems all too obvious. Note also that -- as in Rebecca's careful code -- you should only overwrite _missing_ values, otherwise you can propagate missings and lose what you have. Now let's go back to the assumption that observations occur in pairs. If that is not true, this trick may mess things up. But it is painless to add at the end & _N == 2 bysort PATIENTno : replace whatever = whatever[3 - _n] if missing(whatever) & _N == 2 That way we insist on this being done only for pairs of observations. I find this trick to be slightly but pleasantly amusing when it is the solution, perhaps because it hinges on Stata's treatment of _n and _N and so is a very small insider's joke. Nick On Wed, Feb 6, 2013 at 5:44 PM, Rebecca Pope <rebecca.a.pope@gmail.com> wrote: > Mike, > The way you have specified the -bysort- currently, Stata is looking > within the patient and date of birth for multiple records. You just > want it to look within patient only. > > bys PATIENTno (dtbirth): replace medicalrecordnumber = > medicalrecordnumber[1] if missing(medicalrecordnumber) > > The underlying assumption is that an MRN will always be present when > the DOB is present. If not, you might be better off creating a look-up > table of MRNs and using -merge- to update your missing values. > > preserve > keep PATIENTno medicalrecordnumber > keep if !missing(medicalrecordnumber) > duplicates drop > tempfile mrn > save `"`mrn'"' > restore > merge m:1 PATIENTno using `"`mrn'"', update > > * warning: code not tested > > Cheers, > Rebecca > > On Wed, Feb 6, 2013 at 11:12 AM, Michael Stewart > <michaelstewartresearch@gmail.com> wrote: >> Hi, >> >> I need help with following data where I am trying to combine >> observations for each patient >> >> PATIENTno dtbirth medicalrecordnumber accountnumber >> 1 8/10/1907 1111111 >> 1 . dddddddd >> 2 12/14/1910 222222222 >> 2 . eeeeee >> 3 4/16/1914 33333333 rrrrrrr >> >> >> PATIENTno,medicalrecordnumber & accountnumber -->STRING format >> >> dtbirth-->%td format >> >> >> I need to combine row one and row two for patient 1 so that resultatnt >> row will have information from both rows one and row two >> >> I tried to use subscripting as follows >> >> bysort PATIENTno dtbirth: repalce medicalrecordnumber= medicalrecordnumber[_n-1] >> >> then all values for the medicalrecordnumber are turning to blank spaces >> >> I also tried bysort PATIENTno dtbirth: repalce medicalrecordnumber= >> medicalrecordnumber[1] but it didnt work either. >> >> Can you please help. >> >> -- >> Thank you , >> Yours Sincerely, >> Mike. >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > > > > On Wed, Feb 6, 2013 at 11:12 AM, Michael Stewart > <michaelstewartresearch@gmail.com> wrote: >> Hi, >> >> I need help with following data where I am trying to combine >> observations for each patient >> >> PATIENTno dtbirth medicalrecordnumber accountnumber >> 1 8/10/1907 1111111 >> 1 . dddddddd >> 2 12/14/1910 222222222 >> 2 . eeeeee >> 3 4/16/1914 33333333 rrrrrrr >> >> >> PATIENTno,medicalrecordnumber & accountnumber -->STRING format >> >> dtbirth-->%td format >> >> >> I need to combine row one and row two for patient 1 so that resultatnt >> row will have information from both rows one and row two >> >> I tried to use subscripting as follows >> >> bysort PATIENTno dtbirth: repalce medicalrecordnumber= medicalrecordnumber[_n-1] >> >> then all values for the medicalrecordnumber are turning to blank spaces >> >> I also tried bysort PATIENTno dtbirth: repalce medicalrecordnumber= >> medicalrecordnumber[1] but it didnt work either. >> * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: Need help with combing observations by using by: command along with subscripting***From:*Michael Stewart <michaelstewartresearch@gmail.com>

**References**:**st: Need help with combing observations by using by: command along with subscripting***From:*Michael Stewart <michaelstewartresearch@gmail.com>

**Re: st: Need help with combing observations by using by: command along with subscripting***From:*Rebecca Pope <rebecca.a.pope@gmail.com>

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