OLAP Miner User's Guide


Examples of deviant values in a subcube

The following examples use numeric values to show how OLAP Miner finds deviations in a subcube.

Example 1

Here is a simple two-dimensional subcube:


JAN FEB MARCH APRIL MAY
A 11 12 18 13 13
B 17 15 17000 13 14
C 13 13 15 14 17
D 17 12 16 16 14
E 17 18 15 14 12
F 16 12 17 14 18

OLAP Miner recognizes 17000 as a deviant value with an expected value that is much lower than the actual value. The OLAP Miner algorithm determines that this deviation has a magnitude of 5.

Example 2

What would happen if a 500 value was added to this cube?


JAN FEB MARCH APRIL MAY
A 11 12 18 13 13
B 17 15 17000 13 14
C 13 13 15 14 17
D 17 12 16 16 500
E 17 18 15 14 12
F 16 12 17 14 18

Some mining tools might point out that only the 17000 value is deviant.

If the subcube in this example had an additional entry of 500, OLAP Miner would report both the 500 value and the 17000 value as deviations. The algorithm does not allow the 17000 value to dominate the deviation mining process. If OLAP Miner did not use certain transformations for the data, the 500 value might not be highlighted as a deviation.

In addition, this transformation causes OLAP Miner to focus on the relative differences in the cell value during the analysis, which matches the way that business analysts examine business data.

Example 3

In the following example, the expected value for a cell (D, APRIL) is calculated as higher than the actual value.

The difference between the expected value and the actual value is large enough for this value to be flagged as a deviation.


JAN FEB MARCH APRIL MAY
A 11 12 15 18 13
B 13 15 13 19 14
C 13 13 14 17 14
D 18 19 18 18 19
E 11 12 12 17 12
F 15 15 16 18 16

OLAP Miner finds the cell (D, APRIL) as a deviation with a magnitude of 4. The expected value of the cell is higher because APRIL has slightly higher values (A, B, C, E, and F), but the values for D are flat.

The cell (D, APRIL) does not appear deviant if you look only at row D and column APRIL. However, if you compare the cell (D, APRIL) to all other values in this subcube, then you see that this cell value is deviant.


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