Definition
drill down [phrasal verb with drill verb]: to look for something on a computer or website by moving from general information to more detailed information
Cambridge Dictionary
Drill Down In Data Visualisation
In the context of dashboards and data visualization, drill down refers to the feature of a dashboard that allows the user to explore further details from a more general plot. For example, a plot that shows profit by country could offer the user the possibility to drill down to profit by state within each country.
In the images below, you can see an example of drilling down in Tableau. First, you see the sales by category and then, if you want to further explore a category, you can click on it and check the sales by sub-category. To see the complete example, please check this great dashboard by Alfred Chan.
Why Is Drill Down Important To Your Client?
In the Data School, before we start our projects with external clients, we have internal customers. In our cohort, we had two internal clients, and perhaps one of the most important takeaways from these projects is: to allow your client to drill down into your dashboard. Often, it is by further exploring one aspect of the data that insights appear. Therefore, drilling down can be an essential part of bringing value to your customers.
Below, I show how I offered the possibility of drilling down into a marginal histogram in one of our internal projects. The user story of this plot is about a manager at a call handling station. The manager would like to identify days and months in which the average time to act is particularly long. When he finds this day and month, it would be important for him to explore each call and how long each part of the call lasted. You can achieve that by creating a tooltip with another plot inside it showing the details about that specific part of the plot.
Conclusion
Drill down is a valuable feature in your dashboard because it allows further exploration and increases the probability that your user will get useful insights from your dashboard. Always when you have hierarchical variables, offer the possibility of drilling down and add more value to your dashboards! Enjoy your learning journey!