Often, businesses want to compare year over year values, meaning they want to see how quarters (or months or weeks) in one year compared with the same quarters (or months or weeks) in the previous year.

Tableau exposes Year over Year Growth as one option in the Quick Table Calculations. Here, for example, is a view that demonstrates Sales by Quarter along with the percent difference in sales for a quarter compared with the same quarter in the previous year, as shown:

The second Sum(Sales) field has had the Year over Year Growth quick table calculation applied (and the mark type changed to bar). You'll notice the >4 nulls indicator in the lower-right corner alerting you to the fact that there are at least four null values (which makes sense as there is no 2012 to compare quarters in 2013). If you filtered out 2013, the nulls would appear in 2014, as table calculations can only operate on values present in the aggregated data in the cache (and that data exists post filter).

As easy as it is to build a view similar to the previous one , take care, because Tableau assumes each year in the view has the same number of quarters. For example, if the data for Q1 in 2013 was not present or filtered out, then the resulting view would not represent what you want:

The problem here is that Tableau is calculating the quick table calculation using an addressing of Year and Quarter, and an At the Level of value of Year of Order Date. This works, assuming all quarters are present. However, here the first quarter in 2014 is matched with the first quarter present in 2013, which is really Q2. To solve this, you would need to edit the table calculation to only use year for addressing. Quarter then becomes the partition and, for example, Q2 is compared to previous values in the Q2 partition along the years.