[MUSIC] Welcome back. In our previous lessons, we covered what calculated fields are used for, how to create new fields, and how to use Tableau's quick table calculations. In this lesson, we will focus on custom table calculations for situations when you need to create a calculation that is not already available within Tableau's default table calculations. Let's get started. In this demonstration we will create our own table calculation looking at the difference in sales from the previous partition in our table. To start, let's drag our product category to the rows shelf, and then drag our subcategory to the rows shelf. Then, let's drag a region to the column shelf, and drag our sales field to our table. We now see total sales across regions for each subcategory, and category. In order to find the difference between our regions, we would right click in our data pane, and then select create calculated field. We can title our new field sales difference. And in our calculation let's type zn sum of sales minus lookup z n sum of sales, let's close some parentheses, let's add a minus one, and close our calculation. The zn or zero number function returns a value of zero if the number is null or empty. If the number is not null, then Tableau returns the same number. The lookup function will find your specified value, and the minus one tells Tableau to look one partition back. Now, let's drag our new sales difference field to our worksheet, and now we can see our total sales for each region. But also, the sales difference between each region. This was a simple table calculation, but you can customize table calculations to do whatever you need. I encourage you to take some time to explore the possibilities. So far in this course, you have learned what calculated fields are used for. How to create new fields. How to use Tableau's quick table calculations. And how to create custom table calculations for situations when you need to create a calculation that is not already available within Tableau's default table calculations. In our next lesson, we will discuss Tableau filters. I will show you how to use them to help focus your analysis. Good luck.