Can anybody explain the interaction of Wilkinson and unique?

I was working on one of the Cody questions, and encountered the wilkinson function. In working to solve the problem I was utilizing the unique() function on the wilkinson array, but the results that are returned are not what I would expect. This occurs while using the 'rows' option, not while just using unique.

x = wilkinson(9);
u = unique(x,'rows');

I would expect u to look something like a 9x3 array with 0, 1, and another integer identified in each row, but instead u comes out as a 9x9 array which is the vertical reflection of x.

Does anybody know why this result is generated?

Answer 1

[Walter Roberson]

unique with the rows option does not proceed row by row to give you a list of unique values for the row. If it did do that it would have to return a cell array since the number of unique values could vary from row to row.

The rows option of unique tells you which rows are unique compared to the other rows.