Setting Up a Distinct Count Dimension

How to:

Set Up Distinct Count Measures

Distinct Count Aggregation for measures allows count-oriented measures to avoid the double-counting problem. This would most typically happen in cases such as:

Flag Type Measures. These represent on/off states for a property, such as how many employees have filed their expense statements? or how many trucks are current on inspections for this year? They count how many occurrences are true, or in the case of percentages, display the percent of the entire population that are true. Because the same actual flag can appear multiple times across other dimensions, when rolling up on the Time Dimension, if you did not have a distinct count capability, you would unintentionally double-count the same property.
Event Measures. These count events or the presence or absence of people, equipment, and so on. Because the item or person may be there one week or month, and then return, or stay at the same place for an entire period of time, when aggregating at higher levels of time, you would double-count the same property. An example is hospital stays. A single hospital stay can cross time boundaries, so when rolling up on the Time dimension you would only count each stay once for a particular patient. However, if a patient has another hospital stay within a time frame, then that is a new event that has to be counted separately from the first event.

Distinct Count measures use a special dimension that is otherwise hidden from end users. During measure loads, PMF uses the special dimension to differentiate the counted values and ensure no double-counting when summing values that match along that dimension.

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Procedure: How to Set Up Distinct Count Measures

The following steps explain how to set up Distinct Count measures.

In the Manage page, click the Dimensions panel button.
Click New.

The New Dimension panel opens.
Click the Advanced tab and select the Distinct Count Aggregation check box.

Note: The Distinct Count setting is non-destructive, so you can disable and re-enable it to see the differences in how measure data is processed.
Configure and load at least one dimension to be a Distinct Count differentiator. Click Save and then Load your dimension normally.
For more information on how to use the Dimension Loader, see the PMF Administration Guide.
Note:
- Once you load values into the dimension, these values become the differentiators used to calculate correct counts in Distinct Count processing.
  For example, for the Hospital Event example mentioned previously, you might load all of your patient IDs into this dimension. During Distinct Count processing, PMF would check to see if a patient ID was re-used during any higher level Time aggregation, and prevent that patient from being counted more than once.
- If you set up a dimension to be a Distinct Count differentiator, it is hidden and does not appear in any of the typical locations where you would see a dimension selector.
  For example, you would not see the drop-down of the dimension on the Analysis Designer, the Measure Entry panel, or the drop-downs for Gadget Preferences.
Create a Distinct Count measure. To specify that a measure will use Distinct Count Processing, select the Distinct Processing check box on the Measure panel. Make sure that you have linked exactly one of your Distinct Count differentiation dimensions to the measure by typing its code letter in the Dimensions text box. Click Save once both of these actions are done.

Note: Currently, the Distinct Count capability requires you to use Fixed Targets, not loaded. In the previous example, note that Alternate Time Summary is active, and the Time Summary drop-down is set to Most Recent. Since flags can change to on or off during any time period, setting this to Most Recent enables PMF to always display the most current state within the desired Time level.
Load the measure normally. PMF will store measure data linked to every available matching row for the Distinct Count differentiator dimension, as well as all other linked dimensions, as shown in the following image.
Note:
- For Additive Aggregated measures, the Actual value is always the Distinct Count of the Distinct Count differentiation dimension for that measure.
- For Ratio and Percentage Aggregated measures, the Actual Denominator is always the Distinct Count of the Distinct Count differentiation dimension for that measure. The Actual Numerator is the Distinct Count of the Distinct Count differentiation dimension for that measure, but only if those measure entries have a numerator > 0.
In the example above, which is a Flag type Distinct Count measure, note the Edit on ACTUAL_NUMERATOR, which points to the proper field and sets the value to 1 if the KPI_5 flag field contains Y.
Tip:
- PMF can handle multiple Distinct Count dimensions. Of course, you must still respect the limit of 16 total dimensions.
- Depending on the number of items in your Distinct Count dimension, you might notice a longer loading time for Distinct Count measures.