Power Query how to create and use an ISO Week Number function in Power BI

Steps to create and use a function in Power Query:
1. Define 1 or more parameters.
2. Create query.
3. Create function from query.
4. Invoke function.
Rules for ISO week number:
1. First day of the week is Monday.
2. Each week from Monday to Sunday has the same week number.
3. Week 1 of the year is the week with the first Thursday of the year,
meaning more than half of the days of the week are in week 1.
If January 1st is on Monday-Wednesday 0-2, it will be week 52 or 53 of the preceding year.
If January 1st is on Thursday-Sunday 3-6, it will be week 1 of the current year.
Steps to determine ISO week number:
1. Determine the date of Thursday of the current week.
2. Determine January 1st of the date from step 1.
3. Calculate the number of days from January 1st to the date from step 1.
4. Divide the number of days from step 3 by 7, round down and add 1.

Видео Power Query how to create and use an ISO Week Number function in Power BI канала MarcelBeug