Find the first date

[Qliksense_77]

Hi

I have a dataset from a hospital. Similar to below (except red column). I want to know if a row in the dataset is the first time a specific ID has had surgery.

Therefore I am trying to find the expression for the red dimension?

Id	date of admission	date of surgery	first time surgery per ID?
1	01-01-2021	01-12-2020	yes
2	02-01-2021	02-12-2020	yes
3	03-01-2021	03-12-2020	yes
4	04-01-2021	04-12-2020	yes
5	05-01-2021	05-12-2020	yes
5	05-01-2021	06-12-2020	No
5	05-01-2021	07-12-2020	No

[GaryGiles · Accepted solution]

You need to use the aggr() and FirstSortedValue functions, like this:

=if([date of surgery]=aggr(FirstSortedValue([date of surgery],[date of surgery]),Id),'Yes','No')