Re: st: loops for regions

[Nick Cox <njcoxstata@gmail.com>]

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.

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