Dear all,

It's odd that when I put in the code :
Code:
spmatrix create contiguity W if year == 1995
I get :
weighting matrix W already exists
r(110);

However, when I put in:
Code:
    cap mat drop W
    matrix list  W
I get nothing. Then I just change the name of weight
Code:
    spmatrix create contiguity weight if year == 1995
It says:
weighting matrix in w contains 61 islands

I think that's ok finally but I don't know how to delete the weight matrix W or w. Thanks for any help!

Regards,
Iris