Calculating days between similar or matching rows/events?

Bearcat

Hi everyone, I have a list of events and their dates. I want to calculate the number of days since a matching event happened.

 

For example, I have a list of patients visiting a doctor. I have the first two columns, Name and Date of Visit, but I would like to know how to calculate the third column, Days Since Last Visit. This would return only the number of days since Dave's most recent visit. Any guidance, especially in formula creation, would be appreciated.

 

Name	Date of Visit	Days Since Last Visit
John	6/1/2018	.
Dave	6/14/2018	.
Mike	6/17/2018	.
Mike	6/21/2018	4
Dave	7/1/2018	16
John	7/3/2018	32

gzmorgan0

Bearcat, there are likely multiple methods to do this, but here is my recommendation. Create a column named Date of Last Visit and then find the difference. To get the date of the last visit, I attached a script to the data table.

 

So add new records, run the table script and the table is updated. By keeping the Date of Last Visit, it is easier to verify results.

Note to get days find the difference in the dates and divide by 24*60*60, the number of seconds in a day.

 

I hope this helps.

LastVisit.jmp