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From |
Laura <laura_sendrea@yahoo.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: new variables creation with unbalanced panel |

Date |
Wed, 13 Oct 2010 08:56:43 -0700 (PDT) |

Mr. Kohler and Mr. Booth, Thank you so much for the replies. I have tried the solution suggested by Ulrich Kohler, however I could not make it work yet, which could be, of course, due to my lack of experience. I appreciate the suggestions for further reading a lot. I did not try the second suggestion from Eric Booth yet. It will take me a little time to understand the code. Thank you so much for the time put into this. In my initial email I tried to simplify the problem a little. Here is a more detailed explanation. My panel contains poverty indicators (var x) which as are not available every year and the gaps have various lenghts, among countries and across time. I also have other macro variable which are more or less available yearly (var y). I need to create new variables based on var x, for example, yearly growth, between two consecutive available x's, within a country: growthx(t)=(log x(t)-log x(t-i))/i , where t-i and t are two consecutive years for which var x is available. Also, based on x, for year t, I need the variable initialx(t)=x(t-i), within a country. Based on y, for year t I need the initial value of y which is the value of y in the previous year when x was observed initialy(t)=y(t-i) and the average value of y for all the years between t-i and t. avgy(t)=mean (y(t-i), y(t-i+1)..., y(t)) My simple minded approach is to create a variable that stores the positions where x is observed, for each country. tsset id year sort id year by id (year), sort: gen pos=_n if mean<. Then for each nonmissing value of pos, determine the position of the previous non-missing pos. However, I am not familiar enough with the STATA syntax and I can't make this work. It would be something like this (only it would need to work). by id (year), sort: gen previous=max(range position 1 position-1) if position<. (this statement would have to find the maximum value of pos in the range between the first observation of pos and the (current-1) observation, for each country.) If this can be accomplished, then I could reffer to values of x and y at position previous or in the range (previous position) I don't know if this is actually feasible in STATA or not. Again, many, many thanks for the help. Gratefully, Laura * * 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/

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