====== Measuring Events Duration ======

This guide shown how to log the *duration* of an event and let Google Analytics to report aggregated statistics for it (like the *average duration*).

  - register a //Custom Metric// in the Google Analytics back-end, to log your events //duration//:
    - enter into your Google Analytics web front-end;
    - in the Google Analytics //Property// settings, select //Custom Definitions// and then //Custom Metrics//;
    - select //New Custom Metric//;
    - create a //Custom Metric// with:
      * //Scope//: //Hit//;
      * //Formatting Type//: //Time//
      * (in this example we set the //Name// to //duration//)\\ {{ :ue5-google-analytics:editcustommetric-duration.png |}}
    - **important** take note of the Custom Metric //index// (it's 1-based), from the //Example Codes for This Metric// box;
  - in your application code, log the //duration// metric for the desired events:
    - calculate yourself the event duration (measured in seconds, as a floating point number);
    - add the calculated duration to a logged event (e.g. using ''Record Structured Event''):
      - add it as an event //Attribute//;
      - **important** as key use the string ''cm<index>'', where <index> must be substituted with the Custom Metric //index// discussed above. For example: ''cm1''.\\ {{ :ue5-google-analytics:recordstructuredevent-custommetric.png |}}

GA will now be able to receive and sum all the //durations// you sent.
If you don't see it, double check to pass the Custom Metric //key// as described above.

===== Aggregated statistics =====

We'll now instructs GA to calculate an //aggregated statistics//, the //Average Duration//.

  - create a custom //Calculated Metric//:
    - in your Google Analytics Property //View// settings, select //Calculated Metrics//
    - select //New Calculated Metric//;
    - set the formula to: ''%%{{duration}} / {{Total Events}}%%'' (assuming your Custom Metric is called ''duration'')\\ {{ :ue5-google-analytics:editcalculatedmetric-duration.png |}}

This will allow GA to calculate the average duration for a group of events. The sum of ''duration'' and ''Total Events'' will be computed on the specific grouping of data displayed by Google Analytics.

===== Custom Report =====

You can now use both the //Custom Metric// and the //Aggregated Statistic// in your reports.

The example below is for a //Custom Report// where data are filter for a specific //Event Action// name, with resulting events grouped by the //Event Label// string, with outputs showing the calculate custom //Average Duration// (in addition to the associated //Total Events// and //duration// inputs used by GA to compute the formula).

{{ :ue5-google-analytics:customreportsetup-duration.png |}}

This is an example of the corresponding output:

{{ :ue5-google-analytics:customreportresult-duration.png |}}

GA collects all the events satisfying the //filter//, group them accordingly to our configuration and for each resulting group it sums matching logged //duration// values and then compute the //Average Duration//.