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# st: Mata - extracting various vectors of different sizes in one loop

 From nick bungy To "statalist@hsphsun2.harvard.edu" Subject st: Mata - extracting various vectors of different sizes in one loop Date Thu, 4 Apr 2013 11:26:08 +0100

```I have a mata code that cycles through grid references (eastings, northings) of x entities and calculates for each entity all the other entities which are within a 10km radius of it.
So each individual entity has a row vector, with dimensions anywhere between 1 row (1 firm within 10km radius) and ~80 rows (80 firms within 10km radius). This is throwing up conformity errors when I try to store these vectors into a selection of ~80 variables in Stata.
My thought was to artifically inflate all row vectors to say 100 and fill all of the extra cells in each row vector with 0, then I can extract to 100 variables without conformity errors. I can then clean this up quite easily using Stata functions. I'm not quite sure how to go about this though.
My mata code is the following:

mata:
geoeasta = st_data(., "Geoeast")
geonortha = st_data(., "Geonorth")
n = rows(geoeasta)

density = .
densitytwo = .
densitythree = .
dups   = .

for(i=1; i<=n; ++i) {

d = sqrt((geoeasta:-geoeasta[i]):^2 + (geonortha:-geonortha[i]):^2)
d[i] = .
density = select(d, d[.,1]:<10000)
minindex(density, 80, densitytwo, dups)
st_store(i, ("MSOA1", "MSOA2", "MSOA3" etc etc.), densitytwo)
//This stores the nearest neighbours into our variables, which we defined at the top.

}

end
I suspect I need a line or two below minidex, which inflates densitytwo to a 100 row vector and fills all the extra rows generated with 0. Or perhaps there is a more elegent way?
Many thanks,
Nicholas
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