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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

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

Subject |
st: RE: Re: How to detect the change of i over t? |

Date |
Mon, 9 Feb 2009 12:37:03 -0000 |

Your primary concern should be the unbalanced panels. Does t - 1 mean what it says, or you intend the previous observation? For _balanced panels_, one line of code bysort i (t) : gen become = x == 1 & x[_n-1] == 0 gets you most if not all of the way. The right-hand side (RHS) x == 1 & x[_n-1] == 0 is either true (numerically 1) or false (numerically 0). Benson is right to be concerned about boundary conditions. For the first observation in each panel, we are asking whether x[1] == 1 & x[0] == 0 subscripts being evaluated within panels under the aegis of -by:-. But x[0] is evaluated as missing, and the RHS will be 0 (false). If Benson wants . for the first observation in each panel, then you can do this bysort i (t) : gen become = cond(_n == 1, ., x == 1 & x[_n-1] == 0) For _unbalanced panels_, you may want something more like bysort i (t) : gen become = cond(_n == 1, ., x == 1 & L.x == 0) Nick n.j.cox@durham.ac.uk Martin Weiss See NJC`s FAQ: http://www.stata.com/support/faqs/data/panel.html ********* clear* set obs 20 egen float id = seq(), from(1) to(4) block(5) egen float t = seq(), from(1) to(5) block(1) g x=cond(runiform()<=0.5,0,1) g byte become=. bys id: replace become=cond(x[_n-1]==0 & x[_n]==1,1,0) list, noo sepby(id) *********** Benson Limann > > I am using an unbalanced panel dataset. i is ID and t is time. Every (i,t) > has a characteristic x=0 or 1. > > I want to generate a variable called "become" such that for each (i,t): > > become=1, if x=0 at time t-1, and x=1 at time t > become=0, otherwise > > How to write it? My primary concern is how to deal with the first t for > each i--this observation does not have t-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/

**Follow-Ups**:**Re: st: RE: Re: How to detect the change of i over t?***From:*Austin Nichols <austinnichols@gmail.com>

**References**:**st: How to detect the change of i over t?***From:*Benson Limann <benli2@live.com>

**st: Re: How to detect the change of i over t?***From:*"Martin Weiss" <martin.weiss1@gmx.de>

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