Re: [Gretl-users] matrix indexes question after sort
On Thu, 24 Apr 2008, Franck Nadaud wrote:
I am still developping my spatial tools under gretl, but I have
a difficulty with some matrix functions. My code is an
adaptation of the "brute force" find_neighbor of James LeSage.,,
Well, my problem is that I do not see how to grab not the values
of sorted distances but the indexes of data points. Here is the
code...
See if this does what you're looking for:
<script>
matrix xc = X_COORD
matrix yc = Y_COORD
scalar n = rows(xc)
scalar m = 4
matrix nnlist = zeros(n,m)
matrix idx = transp(seq(1,n))
scalar xi, yi
loop i = 1..n --quiet
xi = xc[$i,1]
yi = yc[$i,1]
dist = sqrt((xc-xi).^2 + (yc - yi).^2) ~ idx
xind = msortby(dist,1)
nnlist[i,] = transp(xind[2:m+1,2])
end loop
print nnlist
</script>
Allin.