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From |
Matthew Baker <matthew.baker@hunter.cuny.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Mata - extracting various vectors of different sizes in one loop |

Date |
Thu, 4 Apr 2013 09:04:05 -0400 |

Nicholas -- I have run into this problem as well, but have a slightly different solution (I'm not sure it's more elegant, though!) One thing that wasn't quite clear from your message was whether or not the values you were computing had to be placed in a particular place or if they could just be listed "from the beginning of a row," so I assumed not. My solution is to create a matrix with a maximal number of columns and then fill it in on the fly, and then get everything into stata using st_view - which has the property that variables can be overwritten from within mata. Anyways: clear all set seed 8675309 set obs 100 mata: // Random lengths for vectors: ni=J(100,1,1) for (i=1;i<=100;i++) ni[i]=round(runiform(1,1)*20)+1 // Random vectors of random lengths placed in the array, // Which will also store a scalar which is length: Z=J(100,30,.) for (i=1;i<=100;i++) { Stuff=runiform(1,ni[i]) length=cols(Stuff) Z[i,1::length]=Stuff } end local zvals forvalues i=1/30 { gen z`i'=. local zvals "`zvals' z`i'" } mata st_view(Ztemp=.,.,"`zvals'") Ztemp[.,.]=Z end On Thu, Apr 4, 2013 at 6:26 AM, nick bungy <nickbungystata@hotmail.co.uk> wrote: > 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 > * > * 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/ -- Dr. Matthew J. Baker Department of Economics Hunter College and the Graduate Center, CUNY * * 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/

**Follow-Ups**:**Re: st: Mata - extracting various vectors of different sizes in one loop***From:*George Vega Yon <g.vegayon@gmail.com>

**References**:**st: Mata - extracting various vectors of different sizes in one loop***From:*nick bungy <nickbungystata@hotmail.co.uk>

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