Power BI Journey: Blog #4

In this blog, I will be changing my approach to how I write the blog. In the previous blogs on Power BI, I was simultaneously doing what Alex is doing in Power BI and then, whenever I encounter issues, I will be writing it directly in the blog and then continued where I left off with the video once I am done. Here, I will watch the video first, take note of important keywords and lessons that Alex emphasizes, and then replicate what he did on the video.

This lesson focuses on DAX or Data Analytics eXpressions. Based on what I understood on the video, DAX can be likened to the formulas associated with MS Excel. And, since Power BI is also a Microsoft product, there are DAX that are similar, if not, the same with what can be found in MS Excel (One example is the IF expression in Power BI).

In this exercise, the process of using DAX was explained starting with creating "New Measure" and then using various DAX to be able to visualize the intended outcome in a table. For example, if we want to visualize the Count of Sales, we can use the expression, COUNT, :

Count of Sales = COUNT('Apocolypse Sales'[Order ID])

This expression counts how many rows are under the Order ID column of the table Apocalypse Sales.

Next, we added a Customer column in order to count the number of orders made by each customer.

Another DAX that was used is SUM. In this particular visualization, we would like to know the total number of sold items for each product.

We can also use mathematical operations for DAX. In this particular visualization, we would like to know the profit made from each customer.

Notice that on the Profit expression:

Profit = (SUM('Apocolypse Store'[Price])-SUM('Apocolypse Store'[Production Cost]))*SUM('Apocolypse Sales'[Units Sold])

we used PEMDAS to calculate the profit for each customers. Notice also its similarity with Excel Formulas.

The next lesson that was discussed was how to create new columns using DAX. In a way, this is like creating one formula at the top most cell and then dragging it down towards the end of the table in MS Excel. In Power BI, this is more efficient using DAX. We click Home > New Column > write the DAX associated with the column. Here are some examples.

Using WEEKDAY:

Using IF:

Notice that when we are using DAX to create new columns, we are using Power Query editor.

Basically, DAX is equivalent to MS Excel Formulas but is more efficient when it comes to executing it on a given table.