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"

@mattab how should those metrics be computed? All goals can be triggered within each visit and some of them even multiple times in a visit. Is time till conversion the time within one visit or since the first visit? Also what about multiple conversions? Are they counted for that metric at all? And if so, is the time the time between the conversions in this case?
Same needs to be defined for numbers of visits till conversion.

@sgiehl as we report the "Days to conversions" in each Goal reports (screenshot below), the metric would be the "Time to conversion" within one visit. it could be clarified in the tooltip and other help that it is the time since the beginning of this visit.