As we have seen with Power BI, we are limited to the space that is given to us within each report page, so we have to make the most of what we are given. Until now, that is. The main purpose of the drillthrough feature is to allow communication between two pages in your Power BI report. You can now create a page within your report that focuses on something very specific and detailed that you might have left out because there wasn't enough room on the page that had visuals relating to this data. Now you can use drillthough filters on that focused page, and your users can right-click on any data point on any other report page and they will be taken to the focused report, which will be filtered by whatever context was in that selected data point. Also, when we set up the drillthrough filters, we have two options. The first option is to set the focused page to only be filtered by specific filters; all other filters that are part of the selected data point when drilling through will be ignored if they are not specified. The second option is where we allow all filters that are part of the selected data point to filter the focused page; this option is known as Keep all filters, and can be toggled On or Off, as seen in Figure 6.1:

For our example, we will be setting the Keep all filters option to On. Let's go ahead and set up the example by copying some of the visuals we created previously in Chapter 5, Visualizing Data, and then moving them into new pages, where we will leverage the drillthrough filter option.

Let's look at, setting up the example:

1. Create two new report pages: the first one should be called Summary Page and the second should be Drillthrough Page.
2. Select the Summary Page report page and add a Stacked Column Chart visual. Resize the visual to take up half of one side of the page.
3. The first field we will select to populate the visual will be our Profit measure, which should be placed under the Value section.
4. Next we will fill the Axis section with our Region Drilldown to bring in the three geographic fields.

5. Lastly, select the Year field from the Date (Order) table to represent our Legend. See Figure 6.2 for reference:

6. Now let's create that focused page by adding visuals to the Drillthrough Page. The first visual we will add is a Table visual. Resize the visual to take up a third of the report page, but leave a small amount of space above the visual.
7. Select the following fields in the order given: StateProvinceName | City | Year (from the Date (Order) table) | Profit.
8. Now add in another visual. Select the Map visual to take up the other two thirds of the report page.
9. In the Location section, choose the City field and place the Profit measure under the Size section.
10. Now we will use the Drillthough filter option. Select and drag the EnglishCountryRegionName field into the Drillthrough section. 

Upon placing a field into the Drillthrough area, you will notice that an image is automatically added to the page in the upper left-hand corner. This is simply an image that has been set with an action to go "back" to the previous page. By selecting the image, you will find that there are quite a few familiar format settings available in the Format Area. One of more common settings to change is the Fill option, which will allow the selection of a color to make the "Back" arrow more visible. Everything is set for the example, so now we can see how the Drillthough option works. Navigate back to the Summary Page and right-click the 2008 (Yellow) section for United States. You will see that there is now an option called Drillthrough, and when you hover the mouse over this new option, you will be presented with a list of available Drillthrough reports. In our scenario, we only have one option, but it is important to note that you can have as many drillthough reports as you desire. Upon left-clicking the Drillthough Page option, you will be taken to that page, and you will see that both visuals have been filtered by the values of United States and 2008. If we were to go back to the Summary Page and make a different selection, those new filters would take effect on these two visuals. Thus, we can see that now we have two report pages that interact with each other. As more and more pages are added to our report, users will always have the option to drillthough to this report with whatever filters they have chosen.