Both fonction work. But I tried to use it in an other chart and I get the following problem. As you can see in the first chart I was counting the ID for each Station. For each station you can have several dates ([date import]). And what I did priviously because I wasn't able to use max() is to count all the ID and divided it by the number of distinct [date import]: Count(ID)/(count(distinct([date import]))).
So I tried both answers you send me because I'm more interested by the number of ID at max([date import]) for each Station instead of my average calculation. But it seems that Qlik will first look for the max([date import]) and then look for the station. The result is on the second picture where you can see that there is only one point.
So how to tell Qlik that for each station I want to look for the max([date import]) and then count the ID. instead of looking for the max([date import]) count the ID and then look for the station?
Qlik tells me there is an error in the expression. I tried a few changes but no results so far. I will dig a little more and see what I can get. Anyway I don't want to bother you for this, you have been more than helpfull!