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Re: st: need mata or perhaps egen help


From   "David Merriman" <dmerrim@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: need mata or perhaps egen help
Date   Thu, 22 May 2008 16:30:33 -0500

Thank very much.  Very elegant and helpful.  I really appreciate it.
and our last names are almost the same!

On 5/22/08, Scott Merryman <scott.merryman@gmail.com> wrote:
> You can use -st_data()- and -st_store()- to move data between Stata
> and mata (see -help m4_stata- )
>
> Below is one way:
>
> clear
> //nearest neighbor matrix
> set obs 20
> set seed 12345
> forv i = 1/20 {
> 	qui gen v`i' = uniform()<.2 in  `i'/l
> 	qui replace v`i' = 0 in `i'
> }
> mata: dist = makesymmetric(st_data(.,.))
> mata: dist
> drop v*
>
> //spending
> set obs 20
> gen spending = uniform()
> gen total =.
>
> //total spending of neighbors
> mata
> spend = st_data(.,"spending")
> spend
> X = dist*spend
> st_store(.,"total", X)
> end
> l
>
>
> Scott
>
> On Thu, May 22, 2008 at 3:06 PM, David Merriman <dmerrim@gmail.com> wrote:
>> I have a set of 584 communities and a square (584x584) matrix D that
>> measures the
>> distance from each community to each community.
>>
>> For each community I also have (584x1) vector (EDI) containing a
>> variable that measures (essentially) the total amount spent on
>> economic development incentives.
>>
>> I have this data for a number of years but I do not think that is
>> important to my programming issues.
>>
>> For each of my communities I want a single variable that measures the
>> total amount spent within a given distance (say 15 miles) on economic
>> development incentives.
>>
>> I can convert my D matrix into a zero/1 matrix
>> (assign zero to home community and and any community more than 15
>> miles distant, 1 otherwise) and Call  this DT
>>
>> Seems I should be then be able to use mata to do the matrix multiplication
>>
>> R=DT*EDI
>>
>> R should be a 584x1 vector with the variable I need.
>>
>>
>> The problem (I think) is that I have never used mata and am having a
>> hard time figuring out how to feed my stata data into mata, do the
>> multiplication and get the result back  to stata.
>>
>> Can anyone tell me how to do this?
>> Maybe there is an easier way to do it with egen or some other stata
>> commands.
>>
>> Thanks
>> Dave Merriman
>>
> *
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>


-- 
David Merriman
dmerrim@gmail.com
*
*   For searches and help try:
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