DAX example from italians - explanantion

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Hi all,

I am absolutely desparate of DAX...I found on youtube video from Italians for beginners (it s look like that is for newbies, but it isn t) and I dont understand mentioned example (https://www.youtube.com/watch?v=6ncHnWMEdic) it starts in 22:22 it takes 10 seconds, the result is on 29:15 (sorry I dont know how to insert picture here or it does not works).. I saw first video, and this example 3x and still nothing, really is this video for beginners? uhh..

My questions are:

Why are used 2 row context and not filter context for each price? 

Why is used 'ROWCOUNT' and not SORTING and then some other funcion?

Why is used 'FILTER' ?

Why is used 'EARLIER'?

thank you so much !!!!!

[Anonymous · Accepted solution]

1. The 1st row context comes from the the table in which you are trying to insert a calculated column. The second row context comes from FILTER, which is an iterator. Hence 2 different row contexts.

2. Sorting does not exist in DAX.

3. FILTER filters data according to a condition returning only the rows that pass the condition.

4. EARLIER is a way to obtain the value from a previous row context. Since VARiables have been introduced, there is now no need to use this function. You can grab the value and assign it to a VARiable that will hold it for the duration of the calculation, whatever the calculation is.

Best
Darek