How do you calculate week over week in tableau in this example I have quantity by week of date and I have the percent difference week over week as a bar chart on the bottom let’s take a look at how to do this in tableau. Let’s start by dragging quantity to rows in our date field to columns. I want my date field instead of year to be week number you’re going to need that to do week over week I’m going to copy the quantity pill by holding Ctrl down and dragging quantity to the right that gives me a second axis I’m going to click on the quantity pill click the drop down quick table calculation and I’m going to use percent difference. Let’s change it to a bar chart. And I have week over week so this last week in the view is down 75 percent I can also drag this to color to color it blue and orange for up or down it is a table calculation so if you click the drop down on sum of quantity and edit table calculation you will need to Define how it’s indexed so now I have it a long week of date if you had other dimensions in here you would have to choose which to check and uncheck based on how you want it to compute in addition you can double click onto the field copy all of this put it into a calculated field. This week over week and see that the calculation is simply sum of quantity minus sum of the previous quantity which is lookup divided by the absolute value of the previous number. Click apply okay and the last thing i’ll show you is how to keep only the last value maybe you’re only looking for a week over week for the most recent week I can use that with a function called last i’ll call this last and show it as last with two parentheses equals zero reply okay and when I drag that last Field onto filters I want only two. And that’s keeping only the most recent week in the view which is December 6 2020 in my case and it’s down 75 percent.