How to Calculate the Previous Sunday's Date in Power BI for Weekly Comments

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Summary: Learn how to calculate the previous Sunday's date in Power BI using DAX and Power Query for effective weekly analysis and reporting.
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How to Calculate the Previous Sunday's Date in Power BI for Weekly Comments

In the world of data analytics, reporting weekly metrics is a common necessity. One frequent task is determining the date of the previous Sunday when analyzing data based on weeks. In this guide, we'll explore how to calculate the previous Sunday's date using Power BI, leveraging both DAX (Data Analysis Expressions) and Power Query techniques.

Calculating Previous Sunday's Date Using DAX

DAX is a powerful formula language used in Power BI for creating custom calculations. Here's how you can calculate the previous Sunday's date with a DAX formula:

Step-by-Step Guide:

Create a New Column:
In your Power BI model, you can create a new calculated column in your data table. Go to the Modeling tab and click on New Column.

Use the DAX Formula:
Enter the following DAX formula to calculate the previous Sunday's date:

[[See Video to Reveal this Text or Code Snippet]]

This DAX formula works as follows:

WEEKDAY([Date], 2) returns the day of the week for the [Date] column, starting from Monday (Monday = 1, Sunday = 7).

The IF function checks if the day is Sunday (WEEKDAY([Date], 2) = 7). If true, it subtracts 7 days from the current date to get the previous Sunday.

If the day is not Sunday, it simply finds the correct previous Sunday by subtracting WEEKDAY([Date], 2) from the current date.

Calculating Previous Sunday's Date Using Power Query

Power Query offers another approach for calculating the previous Sunday's date. It can be particularly useful for performing this calculation during the data transformation process.

Step-by-Step Guide:

Open Power Query Editor:
Launch Power Query Editor by selecting Transform Data from the Home tab in Power BI Desktop.

Add a Custom Column:
Click on Add Column and then Custom Column.

Enter Custom Formula:
Use the following M formula to calculate the previous Sunday's date:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

Date.DayOfWeek([Date], Day.Sunday) returns the day of the week for the [Date] column, starting from Sunday (Sunday = 0, ... , Saturday = 6).

Date.AddDays([Date], -Date.DayOfWeek([Date], Day.Sunday)) subtracts the current day of the week value from the date to get the previous Sunday.

Close and Apply:
After entering the formula, click OK, then close and apply the changes to see the new column reflecting the previous Sunday's date.

Conclusion

Knowing how to calculate the previous Sunday's date in Power BI can greatly enhance your ability to analyze and report weekly data. Both DAX and Power Query provide powerful and efficient methods to achieve this, depending on your workflow and needs. Whether you're preparing dashboards, generating reports, or simply exploring data, these techniques will undoubtedly come in handy.

We hope this guide helps you streamline your weekly data analysis tasks in Power BI. Happy analyzing!