A caution on using Dimensional DSVs in Data Mining – part 2

As a followup to this post I have found that not only does using a table external to the one being mined to provide a grouping fail to actually group within the model, it also confuses the Mining Legend in the Mining Model Viewer.

What I was seeing in the Mining Legend for a node in a Decision Tree was like this:

Total Cases: 100

Category A: 10 Cases

Category B: 25 Cases

Category C: 0 Cases

Category D: 9 Cases

… so the Total cases and the cases displayed didn’t tie up. By digging further using the Microsoft Mining Content Viewer and looking at the NODE_DISTRIBUTION I saw that there were multiple rows for the categories, and the Mining Legend was just picking one of those values.

So if you find youself looking at a node and wondering why the numbers don’t add up – it’s because your grouping hasn’t been used by the model.