multiple observations in the same area

[sungwook kim]

Dear Statalists,

I made a spatial weight matrix with inverse distance weights, which contains missing values. The main reason is that many observations are located in the same area. For example,


LATNUM LONGNUM
Obs A -11.65457 34.1931
Obs B -11.65457 34.1931

As a result, there are missing values in the generated matrix. When I try to run this using :
spmat idistance I LONGNUM LATNUM, id( id ) dfunction(dhaversine) normalize(minmax) replace

I got this error "Two or more observations have the same coordinates"




As an alternative, I used this code from other thread posted in this forum.

clear mata

mata:
id = st_data(., "DHSCLUST")
location = st_data(., ("LONGNUM", "LATNUM"))
N = st_nobs()
M = J(N, N, 0)
for (i=1; i<=N; i++) {
for (j=1; j<i; j++) {
delta = location[i,.] - location[j,.]
M[i,j] = M[j,i] = 1/sqrt(delta*delta')
}
}
M
st_matrix("weightmatrix_women", M)
end

But this also generate missing values in the matrix.
If somebody knows how to sort this out, it would be very helpful for me.

Kind regards,

Kim