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

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: loops for regions |

Date |
Thu, 6 Sep 2012 15:30:20 +0100 |

It's your choice, but you should be able to see that Mata is closer to the mathematics you want to implement. Nick. On Thu, Sep 6, 2012 at 3:26 PM, Chiara Mussida <cmussida@gmail.com> wrote: > Thanks Nick. I will test your suggestion in Stata, since I'm not too > confident with mata. > > On 06/09/2012, Nick Cox <njcoxstata@gmail.com> wrote: >> Thanks. A quick stab at this is that you have two vectors x1 and x2 and go >> >> . mata : >> ------------------------------------------------- mata (type end to >> exit) ----------------------------------------- >> : >> : x1 = (10,10,10,10,10) >> >> : x2 = (12,14,16,18,20) >> >> : sum_x1 = sum(x1) >> >> : sum_x2 = sum(x2) >> >> : a = x2 / sum_x2 >> >> : b = (log(x2) - log(x1)) :- (log(sum_x2) - log(sum_x1)) >> >> : sqrt(sum(a :* (b:^2))) >> .1763637091 >> >> : end >> >> The main thing is not whether I have understood the details but that >> this is a calculator problem; it is just more convenient for a Stata >> user to use Mata for a calculator. >> >> In Stata it could be something like (completely untested code) >> >> sum x1, meanonly >> local sum_x1 = r(sum) >> sum x2, meanonly >> local sum_x2 = r(sum) >> >> gen work = x2 / `sum_x2' >> replace work = work * (((log(x2) - log(x1)) - (log(`sum_x2') - >> log(`sum_x1'))) >> su work, meanonly >> di sqrt(r(sum)) >> >> Nick >> >> On Thu, Sep 6, 2012 at 8:05 AM, Chiara Mussida <cmussida@gmail.com> wrote: >>> The reference is : >>> D.M. Lilien, Sectoral shifts and cyclical unemployment, Journal of >>> Political Economy, 90 (4) (1982), pp. 777–793. >>> >>> The index is defined on page 787. It is a bit more complicated than >>> the herfindahl index. >>> >>> >>> >>> On 06/09/2012, Nick Cox <njcoxstata@gmail.com> wrote: >>>> Did you try >>>> >>>> findit lilien >>>> >>>> Someone may recognise this, but you give no reference or definition. >>>> >>>> Nick >>>> >>>> On Wed, Sep 5, 2012 at 9:52 PM, Chiara Mussida <cmussida@gmail.com> >>>> wrote: >>>>> tried to write my own file since the next step will be, as i hope, to >>>>> compute a Lilien index for each region. I tried to search for a stata >>>>> program but i did not succeed. Does anybody know whether it exists? >>>>> Thanks >>>>> >>>>> On 05/09/2012, Nick Cox <njcoxstata@gmail.com> wrote: >>>>>> The first line confuses the -if- command and the -if- qualifier. >>>>>> >>>>>> I didn't look in detail at later code, as there should be no need to >>>>>> write your own code, as many programs exist. -search inequality- for a >>>>>> start. See also e.g. -ineq- (SSC), -hhi- (SSC). >>>>>> >>>>>> In fact, in many ways this is a calculator problem easily tackled with >>>>>> Mata. >>>>>> >>>>>> . mata >>>>>> : freq = (0, 0, 3, 9, 9) >>>>>> : pr = freq :/ sum(freq) >>>>>> : sum(pr:^2) >>>>>> .387755102 >>>>>> >>>>>> In fact, zero frequencies map to zero squared proportions and can be >>>>>> omitted. >>>>>> >>>>>> This index, although often attributed to Herfindahl by economists who >>>>>> know only their only literature, was in essence invented decades >>>>>> before by Gini. I don't have the reference in my head, but I think it >>>>>> is in Bishop, Y., Fienberg, S.E. and Holland, P.W. 1975. Discrete >>>>>> multivariate analysis. Cambridge, MA: MIT Press. Please trump me by >>>>>> providing a yet earlier reference. >>>>>> >>>>>> Nick >>>>>> >>>>>> On Wed, Sep 5, 2012 at 5:15 PM, Chiara Mussida <cmussida@gmail.com> >>>>>> wrote: >>>>>> >>>>>>> I want to generate a variable herf1 which takes the value of the >>>>>>> below >>>>>>> index for region 1, and thereafter repeat this loop for all the >>>>>>> region >>>>>>> in my dataset. The problem is that with the below command I get the >>>>>>> herf1 index for region 1, which is identycal in value (I tried) to >>>>>>> the >>>>>>> herf2 for region2 whether I repeat this llop for region2, by starting >>>>>>> with "if reg==2, and so forward for all the regions. >>>>>>> >>>>>>> if reg==1 { >>>>>>> tab cat12_2, gen(categ) >>>>>>> forvalues k = 1 2 to 12 { >>>>>>> sum categ`k', meanonly >>>>>>> gen share`k'=r(mean) if reg==1 /*shares of each occ cat on >>>>>>> the >>>>>>> total >>>>>>> occupation, time t*/ >>>>>>> } >>>>>>> } >>>>>>> >>>>>>> gen herf1=(share1)^2 + (share2)^2 + (share3)^2 + (share4)^2 + >>>>>>> (share5)^2 + (share6)^2 + (share7)^2 + (share8)^2 /// >>>>>>> + (share9)^2 + (share10)^2 + (share11)^2 + (share12)^2 /*Herfindhal >>>>>>> Index Region1*/ >>>>>>> the variable reg takes 1 for region1, 2 for region2...up to 20 for >>>>>>> region20. In other words, Stata does not compute the specific index >>>>>>> for each region, but the same index region by region. * * 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/

**References**:**st: loops for regions***From:*Chiara Mussida <cmussida@gmail.com>

**Re: st: loops for regions***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: loops for regions***From:*Chiara Mussida <cmussida@gmail.com>

**Re: st: loops for regions***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: loops for regions***From:*Chiara Mussida <cmussida@gmail.com>

**Re: st: loops for regions***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: loops for regions***From:*Chiara Mussida <cmussida@gmail.com>

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