To create a similar chart, create a new report with a chart section including the time dimension and any other dimension you want to report on (set these to filter or column) and then add the unique users metric. You can use the chart settings tab to change the way the chart looks.
Take a look at the DMI documentation which contains a lot more information around creating such reports. https://community.dynatrace.com/community/display/...
The reason why unique users metric is not available for historical time ranges is that it would require DCRUM to keep a data for all those users for a very long time. The database size and the time to render such a report would grow significantly.
It could be an idea for extending product capabilities, but even to keep data with just one day resolution for historical time ranges we would first require to identify what kind of aggregates are required and keep information for those aggregates only.
For other resolutions it would become virtually impossible to properly compute unique users. Example: unique users values during the week were [Mon: 10, Tue: 12, Wed: 20: Thr: 14, Fri: 23, Sat: 10, Sun: 2]. What would be the unique users count for the whole week? We can only tell it would be something between 23 (everyone who visited the site this week also visited the site on Friday) and 91 (each user never returned to the site during this week).
The solution could be to use Splunk or Elastic integration to export data. It should work for one day resolution. For other resolutions to work you would need to export raw data for aggregates that you are interested in.
Unique users may be the wrong metric for what we are trying to do. We just need the volume of users.
If a users comes in multiple times a day, week, or month, we need to count him/her to the total anyways.
I was just wondering if "User sessions" metric wouldn't do the trick?
User sessions = "The number of user HTTP sessions. The count can be identified by information contained in intercepted HTTP cookies or by HTTP authorization."