# Create a formula indicator

Create a formula indicator to use the historic data of other indicators and analytical functions to produce a computed score.

Before you begin

Formulas are often used to:
• Calculate ratios and percentages.
• Combine data from different applications.
• Build predictive indicators based on historic performance.
Note: You must have a license for Performance Analytics to create indicators.

Procedure

1. Navigate to Performance Analytics > Formula Indicators.
The fields of a formula indicator are similar to an automated indicator except for the condition. Formulas can consist of other indicators, constants, and time series, or any combination of these.
2. In the Formula section of the Indicators form, click the Browse for an indicator link.
3. Select an Indicator to display.
Note: You cannot delete any indicators, such as automated indicators, that are used in a formula. You must change or delete the formula indicator before you can delete any indicators used in the formula.
4. (Optional) Select a Breakdown and breakdown Element to filter the indicator data.
You can select an additional breakdown and breakdown element to further filter the data.
5. (Optional) Select a Default time series to use when aggregating the data.
6. (Optional) Select the Apply time series to result check box.

When selected, the indicator calculates the formula first, then applies the time series calculation to the result. For example, when calculating the weekly average incident resolution time using the formula ```Total time to resolve incidents / total incidents resolved```, the formula first calculates the average incident resolution time for each day, then the average of those times. Each day is given equal weight, leading to an unweighted average.

When cleared, the indicator applies the time series to each component individually before calculating the score. Using the average incident resolution time example, clearing the check box results in a weighted average. The formula first calculates the weekly sum of the total time to resolve incidents and the weekly total number of incidents, then uses those values to calculate the weekly average time to resolution.

7. (Optional) Clear the Allow breakdowns check box to prevent breakdowns from applying to this formula component.
8. Click Select.
The Formula field is automatically populated based on your selections.
9. Modify the Formula as needed. Enter any operators or numbers to include in the formula. Use valid operator symbols, such as +, -, /, %, >, <.

For example, if you want to calculate the average age of open incidents based on summed age of open incidents and number of open incidents, you could use the following formula: ```[[Summed age of open incidents]] / [[Open incidents]] / 24```

Use the script variables `score_start` and `score_end` to refer to the start and end of the data collection period, respectively.

Formulas support multi-level breakdowns. For indicators that have Collect breakdown matrix enabled, it is possible to drill down to the second level in the detailed scorecard on the Breakdowns tab. For example, Closed incidents by Category, and then by Priority, or vice versa.

## Prevent a formula component from following breakdowns

You can prevent certain formula components from being broken down when a user applies a breakdown to the formula indicator.

When you apply a breakdown to a formula indicator, such as on a breakdown dashboard, the selected breakdown applies to all formula components. You prevent certain components from being broken down using the syntax {{Indicator}}. You can also prevent a formula component from following breakdowns by clearing the Allow breakdowns check box in the Browse for an indicator popup.

For example, consider the formula [[Incidents]] / [[Customers]]. If you apply a region breakdown to this indicator, and specify EU as the breakdown element, the formula indicator returns scores using the formula [[Incidents > region = eu]] / [[Customers > region = eu]]. However, to view the EU incidents divided by the total number of incidents across all regions, you can write the formula as [[Incidents]] / {{Customers}}. Using the {{Indicator}} format causes the Customers component to ignore breakdowns. This way, when you apply the region breakdown with the EU breakdown element, this formula indicator is equivalent to the formula [[Incidents > region = eu]] / [[Customers]].

You can specify a breakdown within a component itself, such as [[Incidents]] / {{Customers > importance = high}}. In this example, the formula denominator is always broken down to include only the high-importance customers. Any breakdown applied to the formula indicator, such as the region breakdown, does not apply to the Customers component.

## Breakdown matrixes in formula indicators

Formula indicators inherit breakdown matrixes from indicators in the formula.

If all the indicators in the formula collect breakdown matrixes, 2nd level breakdowns are available for the formula indicator. If none of the indicators in the formula collect breakdown matrixes, 2nd level breakdowns are not available for the formula indicator. If only some of the indicators in the formula collect breakdown matrixes, only those indicators can be broken down at a 2nd level.

For example, consider a formula indicator with the following formula:

`[[Summed age of open incidents]]/[[Number of open incidents]]/24`

Both the Summed age of open incidents and the Number of open incidents indicators have breakdown matrixes collected. In the detailed scorecard for the formula indicator, you break down the scores first by Category=Software and second by Priority=High(2). The result is a score of 170.

Now consider the same formula indicator, but the breakdown matrix is not collected for the Number of open incidents indicator. The result is a score of 11.