The Round Extra transformation allows numbers to be rounded, and extra numbers either side of the rounded number created, so that numbers that are close to one another can be brought into the same clusters.

Note that Round Extra cannot be used in comparisons.

Use the Round Extra transformation if you have numerical data with varying degrees of accuracy, and you want to cluster using an approximation of each numeric value, adding extra cluster values either side of the rounded value.

Round Extra is useful in order to avoid problems with rounding to single numeric values. For example, if you want all records with a numeric value within a given difference from another numeric value to be in the same cluster, this can be difficult to achieve when rounding all numbers to a single value.

For example, you may have a rule that all numbers that are within 10 of each other must be in the same cluster, so the numbers 32 and 41 should be in the same cluster. However, if using the conventional Round transformation, rounding down to the nearest 10 will place them in groups 30 and 40 respectively, as will rounding nearest, and rounding up will place them in groups 40 and 50. If you use Round Extra however, you can ensure they are in the same groups by generating multiple cluster values for each input value. In this case, if the values 32 and 41 are rounded to the nearest 10, then 32 will be placed in groups 20, 30 and 40, and 41 will be placed in groups 30, 40 and 50.

The following table describes the configuration options: