I had a huge problem with WEIGHT module in IDRISI. Nothing worked. The message was "Unexpected error conditions encountered. Please check the integrity of the operations performed, the data files used, and the amount of disk space available." The operation ended prematurely, before I could get the weights for my factors. So I looked into IDRISI help and found this:
"The weights generated by this module are produced by means of the principal eigenvector of the pairwise comparison matrix. A good approximation can also be generated by hand as follows: First, fill out the entire matrix by making each entry in the upper-right triangular half equal to the reciprocal of the corresponding entries in the lower-left. Sum each column to get a column marginal total, then generate a matrix by dividing each entry by the marginal total in its column. Each column of this matrix will be an estimated set of weights. Average the weights across the rows. The result will be very similar to that achieved using the principal eigenvector."
So that's what I did.
The matrix that I used was:
1 7/5 7/11 7/2 7/8
5/7 1 5/11 5/2 5/8
11/7 11/5 1 11/2 11/8
2/7 2/5 2/11 1 2/8
8/7 8/5 8/11 8/2 1
-----------------------
33/7 33/5 3 33/2 33/8 (marginal column sum)