Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
From | Nick Cox <njcoxstata@gmail.com> |
To | statalist@hsphsun2.harvard.edu |
Subject | Re: st: differentiating between groups of records with same date |
Date | Mon, 30 Jul 2012 11:49:30 -0500 |
bysort patient_no diag_date: gen freq = _N See also SJ-2-1 pr0004 . . . . . . . . . . Speaking Stata: How to move step by: step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox Q1/02 SJ 2(1):86--102 (no commands) explains the use of the by varlist : construct to tackle a variety of problems with group structure, ranging from simple calculations for each of several groups to more advanced manipulations that use the built-in _n and _N Nick On Mon, Jul 30, 2012 at 10:20 AM, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote: > Hi all, > > I have a group of patients who are in a dataset of cancers. Each patient may have more than one cancer diagnosed, and so may be present in my dataset a number of times. Each patient has a unique patient identifier, and each cancer has a unique cancer identifier. Each row of data is cancer specific, but does contain the patient identifier. It is possible that a patient has 2 cancers diagnosed on the same day in my dataset. What I would like to do is generate a flag next to each record to show against each cancer the number of cancers diagnosed on the same day. > > My data are like this: > > patient_no cancer_no diag_date surgery_date > 9512834 0484360 21may1994 21may1994 > 9512834 0484358 21may1994 21may1994 > 9512834 0483234 26apr2000 21may2000 > 9512834 0483233 26apr2000 > 0000057 0000057 19jul2009 19jul2009 > 0000060 0000060 02nov2009 24nov2009 > 0000074 0000074 21sep2009 22nov2009 > > > For example, patient 9512834 had 2 cancers diagnosed on 21may1994 and so for cancer_no 0484360 and 0484358, I would like to generate a new variable with the value 2 against each record. Similiarly patient 0000057 has only one cancer diagnosed, and so the new variable would contain 1. > > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/