So one way to do this is like so....
First I created a Day level of your Date Time (so just truncated down to day)
I can then use this field to work out any average for a day like so
[Average Crimes Per Day]
As this is an aggregate calculation it will just work for whatever level we have in our Viz, and for any filters.
So I bring in your datetime, and select the hour (part) level...and that's it
I've also added an extra viz 'Calc Check' so you can see what the calculation is doing. Looks like you don't want to be out in Chicago at midnight on New Years Eve!!!
Hope that is what you were after and makes sense
Chicago Example_SR.twbx 14.1 MB
Thank you very much!