New metrics "Time to conversion" and "Visits to conversion" for Goals and Ecommerce #6105

Edit 2019:

Summary

The following 2 new features would be very valuable:

• Time until conversion (eg. 5 days or 1h 15min or 1min 40s)
• Number of visits until conversion

Original

The goal of this ticket is to add a new metric processed and displayed for each goal, and ecommerce conversions. This metric is the time it takes for a visit to reach this particular goal.

Example In the Piwik reports for our website, we have a goal called Download Piwik, so in the goal report there would be a sparkline "Time to Download Piwik 02:15"

This nice idea originates from an email:

How much time did it take for a customer to reach a goal (in minutes and seconds)?

I could only read it in the customer log if i moved the mouse over the first action and the goal action and calculated the difference.

This is a very important measure for every website.

Thanks

Tasks

• find a name for the sum metric sum_time_to_conversion and a name for the processed metric, eg. avg_time_to_conv
• aggregate this metric during archiving, for each goal, for goals overall, and for ecommerce conversions
• add metric to API responses for goals metrics
• add to metadata API
• display in the goal overview, a new sparkline showing the metrics similarly to how we currently display the site speed metric: 0.41s average generation time
• update the reference API page to document this new metric

See also #2029

great idea!
Doing this one may also add "number of visits until conversion"