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From |
Nabarun Dasgupta <nabarund@gmail.com> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: Re: brace counting for person-time |

Date |
Sun, 03 Mar 2013 22:58:50 -0500 |

Of course the answer comes to you after you reach out. The solution that is working for me: 1. Convert ender to 1/-1 instead of 0/1 and use sum() to create a running total 2. Figure out the number of NON-EXPOSED days (including ends of the month) using the running total 3. Subtract from the known number of days in the month On 3/2/13 5:26 PM, Nabarun Dasgupta typed: > > >Dear STATALIST: > >I would greatly appreciate your help and haven't seen exactly what I need >in the archive. I am trying to count the person-days exposed for a single >patient in a given month over multiple overlapping Rx records. The correct >number of days exposed is 26 in the example data below. I tried a "brace >counting" approach, so the variable _ender_ is zero at the start of the Rx >period, and one for the last day of the period. Hence there are eight >records for four prescriptions. One solution would be to calculate the >days in between each _bracedate_ and only add up the unique days between >braces, but I can't figure out how to create a counter that identifies >only the exposed periods. Note that rxno 5061 was only for one day, making >things trickier. > > > >start stop rxno ender bracedate >5-Jan-11 12-Jan-11 2248 0 5-Jan-11 >12-Jan-11 26-Jan-11 3645 0 12-Jan-11 >5-Jan-11 12-Jan-11 2248 1 12-Jan-11 >19-Jan-11 30-Jan-11 2261 0 19-Jan-11 >25-Jan-11 25-Jan-11 5061 0 25-Jan-11 >25-Jan-11 25-Jan-11 5061 1 25-Jan-11 >12-Jan-11 26-Jan-11 3645 1 26-Jan-11 >19-Jan-11 30-Jan-11 2261 1 30-Jan-11 > > >Generalized schematic of the brace counting approach is below, but I am >open to other solutions. Creating a dummy variable for each date and using >0,1 is not an option as far as I can tell because of the number of >prescription records (55 million) and length of time (3 years). > > > >Overlapping intervals: > > (-------------------) > (----------------------) > (---) > (---------------------) > (-----------------) > > Consolidated: > > (-----(-------------)-(-----)----------------) (----(---)--------) > > > >Your help is genuinely appreciated! > >Best, >Nabarun > >----- >Nabarun Dasgupta >Department of Epidemiology >Gillings School of Global Public Health >& Injury Prevention Research Center >University of North Carolina >Chapel Hill, NC 27599 USA > > * * 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/

**References**:**st: brace counting for person-time***From:*Nabarun Dasgupta <nabarund@gmail.com>

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