<>
For a start, the # of obs is accessible via "c(N)" throughout your
journey... No need to put it in a -local- or -scalar-
This -for- loop you are using used to be popular, as I understand from old
SJ articles, but has since been superseded by -foreach- and - forvalues-.
See http://www.stata-journal.com/sjpdf.html?articlenum=pr0005
It lives on in -mata-, though, but you employ the old -matrix- language...
HTH
Martin
_______________________
----- Original Message -----
From: "Susan Olivia" <[email protected]>
To: <[email protected]>
Sent: Wednesday, May 13, 2009 7:53 PM
Subject: st: Matrix manipulation help
Dear Stata list,
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.
Thanks,
Susan
****************************
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/
*
* 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/
