Context Filters are applied to the data rows before any other filters. They are limited to views, but they can be applied on selected sheets. They define Aggregation and Disaggregation of data in Tableau
Step 1: Drag the subcategory dimensions to the row shelf and the measure sales to the column shelf. Now choose the horizontal bar chart as chart type and again drag the sub category dimensions to the filter shelf. Then we will get the following chart.
Step 2: Right-click on the Sub-Category field in the filter shelf and go the Top fourth tab. Choose the option field, from the next drop-down and choose the option Top 10 by Sales Sum as shown in the following screenshot.
Step 3: Drag the dimension Category to the filter shelf. Give right-click on the general tab to edit and under that choose Furniture from the list. As you can see the result shows three subcategories of products.
Step 4: Right-click the Category: Furniture filter and select the option Add to Context. This produces the final result, which shows the subcategory of products from the category Furniture which are among the top 10 subcategories across all the products.