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

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Extract year of maximum production |

Date |
Sat, 20 Oct 2012 19:59:53 +0100 |

For completeness, note reshape long timber, i(county) j(year) bysort county (timber) : gen whenmax = year[_N] Nick On Sat, Oct 20, 2012 at 3:36 PM, Daniel Escher <descher@nd.edu> wrote: > Nick, that worked perfectly. Thank you so much! > > egen maxprod = rowmax(timber1910-timber2010) > recode maxprod 0 = . // I recoded counties without production to > missing for now > gen whenmax = "" > qui forval y = 1910/2010 { > replace whenmax = whenmax + "`y' " if timber`y' == maxprod > } > gen when = real(whenmax) if wordcount(whenmax) == 1 > > *Yes, 1910-2010 is 101 years. > *I didn't have any duplicates/ties to worry about > > On Sat, Oct 20, 2012 at 4:18 AM, Nick Cox <njcoxstata@gmail.com> wrote: >> There is a review of working row-wise in >> >> SJ-9-1 pr0046 . . . . . . . . . . . . . . . . . . . Speaking Stata: Rowwise >> (help rowsort, rowranks if installed) . . . . . . . . . . . N. J. Cox >> Q1/09 SJ 9(1):137--157 >> shows how to exploit functions, egen functions, and Mata >> for working rowwise; rowsort and rowranks are introduced >> >> which is accessible to all under the SJ's 3-year rule. -search >> rowwise- to get a clickable link. >> >> You have already alluded to two key principles in this territory >> >> 1. A -reshape long- can make a row-wise problem easier. >> >> 2. There are -egen- functions for row problems. >> >> Even more important than #2 is >> >> 3. You can solve many problems with a loop over variables. >> >> as #2 is just an application of #3. >> >> With 3000-odd counties there may well be ties, i.e. counties for which >> two or more years show the same maximum. >> >> Let's be alert to that amd use a slightly odd technique. (Others will >> be suggested by my paper referred to above.) Starting with your idea >> >> egen maxprod = rowmax(timber????) >> >> let's initialise a string variable >> >> gen whenmax = "" >> >> Now whenever we find a year when the maximum occurred we add that year >> to our string >> >> * isn't that 101 years? no matter >> qui forval y = 1910/2010 { >> replace whenmax = whenmax + "`y' " if timber`y' == maxprod >> } >> >> Note the extra space in the " " above. >> >> In most counties there will be a single year when there was a maximum >> >> gen when = real(whenmax) if wordcount(whenmax) == 1 >> >> And you can look at the cases with ties to think what you want to do with them: >> >> l county whenmax if wordcount(whenmax) > 1 >> >> Notes. >> >> To extract words from a string, use -word()-. >> >> If you have counties with 0 values, they might as well be -mvdecode-d >> to missing before you calculate your maximum. Extreme case: a county >> with 0s in every year; iit is absurd to say that the maximum >> production occurred in every year. (Or you might just -drop- such >> counties.) >> >> Similarly, this technique assumes that there aren't so many ties that >> the years can't be fit in a -str244- variable and if that's wrong you >> may need a different technique >> >> Nick >> >> On Sat, Oct 20, 2012 at 4:10 AM, Daniel Escher <descher@nd.edu> wrote: >>> I have 100 years of timber production data for all counties in the US >>> (~3,100). The data are currently in wide format - i.e., timber1910, >>> timber1911 ... timber2010 (but I can switch them to long if needed). >>> >>> I would like to extract the year of maximum timber production for each >>> county and put that year in a variable called "peakyr." Two things I >>> thought might be helpful: 1) I can use -egen newvar = rowmax...- to get the >>> maximum value of a row. 2) I can separate the stub and the year in the >>> variable name using the -substr- function. Unfortunately, I don't know how >>> to make those two processes "talk" to each other - if they are even the >>> right ones to use. >>> >>> Stata/IC 12.1 for Windows (32-bit) >>> Revision 01 Oct 2012 * * 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: Extract year of maximum production***From:*Daniel Escher <descher@nd.edu>

**Re: st: Extract year of maximum production***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: Extract year of maximum production***From:*Daniel Escher <descher@nd.edu>

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