What is a DAX function?
DAX (Data Analysis Expressions) is a formula language used in Power BI and Excel. DAX functions help you to create custom calculations and aggregations for data models. The WEEKDAY function is one of the many DAX functions available in Power BI.
Understanding the WEEKDAY function
The WEEKDAY function returns the day of the week as a number, based on a given date. The function accepts two arguments:
* Date: The date for which you want to find the day of the week.
* Return type: A number that indicates the numbering system for the day of the week.
By default, WEEKDAY returns a number between 1 and 7, where 1 is Sunday and 7 is Saturday. However, you can modify this to use different numbering systems.
Using the WEEKDAY function in Power BI
Now that you understand the basics of the WEEKDAY function, it’s time to see how you can use it in Power BI. Let’s look at some examples:
Example 1: Finding the day of the week
To find the day of the week for a given date, use the following formula:
DayOfWeek = WEEKDAY(‘Table'[Date])
In this example, 'Table' refers to the name of the table containing the Date column. The formula returns a number between 1 and 7, where 1 is Sunday and 7 is Saturday, depending on the date in the Date column.
Example 2: Customizing the numbering system
If you want to use a different numbering system, you can modify the return type argument. For example, to return a number between 0 and 6, where 0 is Sunday and 6 is Saturday, use the following formula:
DayOfWeek = WEEKDAY(‘Table'[Date], 2)
Example 3: Using the DAY function with WEEKDAY
You can also use the DAY function with WEEKDAY to return the day of the week in a specific format. For example, to return the day of the week as a text value, use the following formula:
DayOfWeek = SWITCH(WEEKDAY(‘Table'[Date]), 1, “Sunday”, 2, “Monday”, 3, “Tuesday”, 4, “Wednesday”, 5, “Thursday”, 6, “Friday”, 7, “Saturday”)
In this example, the SWITCH function is used to return the day of the week as a text value, based on the number returned by WEEKDAY.
The WEEKDAY function is a powerful tool that can help you analyze and visualize data in Power BI. By using the function, you can easily find the day of the week for a given date, customize the numbering system, and even return the day of the week in a specific format. With this knowledge, you can take your data analysis to the next level and make more informed decisions based on your findings.