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

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: set obs by level (of multiple variables)? |

Date |
Thu, 17 Jan 2013 17:33:39 +0000 |

Rebecca gives good advice. The underlying principles are discussed in FAQ . . . . . . . . . . . . . . . . . . . . . . . True and false in Stata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox 8/05 What is true and false in Stata? http://www.stata.com/support/faqs/data-management/ true-and-false/ 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 On Thu, Jan 17, 2013 at 4:30 PM, Rebecca Pope <rebecca.a.pope@gmail.com> wrote: > bysort TCATOG sex : gen first2 = (_n==1) > > That tests whether it is the first observation or not & returns 1 if > true, 0 otherwise. On Thu, Jan 17, 2013 at 10:24 AM, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote: >> Nick thanks for your help. This does what I need, although, rather than duplicating the last record, duplicating the first might be more helpful as this would contain much of the baseline information I already hold. I naively thought that this would work!!: >> >> bysort TCATOG sex : gen first2 = _n - but I have 1-20 rather than 1 followed by 0 >> >> I could then use replace first2 = 0 if first !=1 - but I'm assuming there is a better way? Nick Cox >> The syntax diagram for -set- does not indicate support for -by:- and >> >> 1. Whatever is not permitted should be considered forbidden. >> >> 2. Less gnomically, there is a really good reason for this. In essence, -set- is about global settings, and even if what you are asking for makes sense -- as it does here -- -set- and -by:- don't mix naturally. >> >> See help for -expand-, -expandcl-, -expandby- (SSC). >> >> bysort stage sex : gen last = _n == _N >> expand 2 if last >> sort stage sex >> ... if last On Thu, Jan 17, 2013 at 3:08 PM, Tim Evans <Tim.Evans@wmciu.nhs.uk> wrote: >>> I'm trying to insert extra observations in my dataset - I've calculated survival and wish to graph the results but the data start from less than 100%, but I'd like the graph to graph from time 0 and thus 100%. My dataset is split by gender and stage so I need something that inserts an observation for say males & stage 1, males stage 2, females stage 1 and females stage 2. >>> >>> Unfortunately, while this will provide me with an observation >>> >>> set obs `=_N+1' it does not support this: >>> >>> bysort stage sex: set obs `=_N+1' >>> >>> Does anyone have an idea how I might do this in Stata 11.2? * * 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: set obs by level (of multiple variables)?***From:*Tim Evans <Tim.Evans@wmciu.nhs.uk>

**RE: st: set obs by level (of multiple variables)?***From:*Tim Evans <Tim.Evans@wmciu.nhs.uk>

**Re: st: set obs by level (of multiple variables)?***From:*Rebecca Pope <rebecca.a.pope@gmail.com>

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