Call out positions of selected data points in your Tableau view using Drop Lines
I am barely using gridlines on my charts. In fact I didn’t even know that Tableau Software has an option to show and format gridlines. Hence I started the original introduction to this post as follows:
Unlike Microsoft Excel, Tableau Software does not provide an option to display gridlines on charts. Tableau allows you to define so called row and column dividers, but only for categorical data, i.e. dimensions.
This statement is totally wrong: Tableau offers gridlines (Format | Lines | Grid Lines) and Rich was kind enough to correct this in the first comment to this post. Thanks Rich. My fault. I apologize for the confusion.
But still: gridlines are very often nothing else than chart junk as Stephen Few points out in this excellent article: Grid Lines in Graphs are Rarely Useful. Tableau has something way more useful than gridlines: the interactive Drop Line.
Today’s short Tableau Quick Tip #4 introduces this extremely helpful interactive feature of Tableau.
Let’s say we look at the development of the German DAX during the last (almost) 25 years, i.e. since 1988:
So far, so good. Now, what if we want to put some of the highs and lows (or any given data point) into the context of the whole view, i.e. all other data points?
E.g. let’s have a closer look at the lowest point since 2000: March 2003. We can see from the line chart that the DAX approximately fell down to the level of 1995, but can you immediately see whether it has ever been higher than this before 1995?
A Drop Line can help to explore the data on a more detailed level.
How to Use Drop Lines in Tableau
This is probably the most easiest and simplest step-by step I ever published:
Right click somewhere in the view and select Drop Lines:
Right click again and select Edit Drop Lines:
In the upcoming dialog window, define which axis / axes you want the line drop to, whether you want to show it always or only when selected and whether or not you want to show the labels close to the axes:
Caution: don’t select "Drop when Always” in a view with a lot of data points (like in my example). This will not only totally clutter the view, it will also take a considerable time until Tableau will update the chart.
That’s it already. A couple of mouse clicks and you can select any data point in the view and get the drop line:
Now it is much easier to put the selected data point into the context of the entire DAX development over the years. We now see that the DAX have been above the selected level in 1993 and 1994, but only twice and only for a very short period.
Drop lines are a very helpful interactive feature, especially for line, area and scatter charts with a lot of data points. If the data and the views are suitable, drop lines can considerably improve the interactivity of your view / dashboard and make data analysis and storytelling much easier.
As shown above, Tableau drop lines are only a few clicks away. One of the best things about it is the fact that the drop lines will automatically also be available on each dashboard you are using this view on. And it will not interfere with any click-on actions you may have defined.
Microsoft Excel has drop lines too and it allows you to use them in line and area charts as Jon Peltier describes in this great post: Drop Lines in Excel Line and Area Charts. However, Excel’s default drop lines are static. In one of the next posts I will describe how to create interactive drop lines in Microsoft Excel charts.