Countif comparing dates in Tableau

Question

I am trying to create a table where it only counts the attendees one one type of training (rows) if they attended another particular training (column) AFTER the first one. I think I need to recreate a countif function that compares the dates of the trainings, but not sure how to set this up so that it compares the dates of the row trainings and column trainings. Any ideas?

Edit 3/23

Alex, your solution would work if I had different variables for the dates of each type of training. Is there a way to construct this without having to create new variables for each type of training that I want to compare? Put another way, is there a way to refer to the rows and columns of the table in the formula that would compare the dates? So, something like "count if the start date of this column exceeds the start date of this row." (basically, is there something like the Excel index function in Tableau?)

It may help to see how my data is structured -- here is a scrubbed version: https://docs.google.com/spreadsheets/d/1YR1Wz-pfGHhBxDQDGYgmemLGoCK0cSvKOeE8w33ZI3s/edit?usp=sharing

The "table" tab shows the table that I'm trying to create in Tableau.

Answer 1

Define a calculated field for your condition, called say, trained_after, as:

training_b_date > training_a_date

trained_after will be true or false for each data row depending on whether the B training was dated later than the A training

If you want more precise control over the difference between the dates, use the date_diff function. Say date_diff("hour", training_a_date, training_b_date) > 24 to insist upon a short waiting period.

That field may be all you need. You can put trained_after on the filter shelf to filter only to see data rows meeting the condition. Or put it on another shelf to partition the data according to that condition. Or use your field to create other calculated fields.

Realize that if either of your date fields is null, then your calculated field will evaluate to null in that case. Aggregate functions like Sum(), Count() etc ignore null values.