# st: RE: RE: Matrix manipulation help

 From "Nick Cox" To Subject st: RE: RE: Matrix manipulation help Date Wed, 13 May 2009 19:27:48 +0100

```-nearest- on SSC has relevant (pre-Mata) code.

I thought Michael Blasnik had written something more efficient but I
can't find it or -findit- quickly.

Nick
n.j.cox@durham.ac.uk

Nick Cox

By the way, hasn't this been done before?

Nick
n.j.cox@durham.ac.uk

Susan Olivia

Can I get programming advice how to create a NxN distance
matrix using the information on latitude and longitude.

Below is what I attempted to do in STATA, but it didn't
work. Would be great if I can get any advice on how to
improve this code.

****************************
qui set obs 1000

gen xcoord = uniform()*100
gen ycoord = uniform()*100

mkmat xcoord ycoord

local N=_N
scalar N = _N

matrix latlong= xcoord,ycoord

matrix D = J(`N',`N', 0)

* looping through the rows and columns of the matrix D, to
get distance pair for each observations

for(i = 1; i <=N; i++) {
for(j = 1; j<=N; j++) {
if (i!=j){
D[i,j]=
((xcoord[i]-xcoord[j]^2+(ycoord[i]-ycoord[j]^2)^0.5

}
}
}

*
*   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/
```