Tableau Course
Area and Scatter Charts
Area charts show cumulative volume over time with filled colour beneath the line. Scatter plots reveal the relationship between two measures — whether they move together, oppose each other, or have no connection at all.
Area Charts — Volume Over Time
An area chart is a line chart with the region between the line and the axis filled with colour. The filled area emphasises cumulative magnitude — it makes it visually obvious not just that values are rising, but how much total volume has accumulated. Area charts work best when you have one or a small number of series and the total filled area carries meaning.
The stacked area chart is a common variant — multiple series are stacked on top of each other so the total height of the filled area represents the combined total, while individual coloured bands show each series' contribution to that total.
Stacked Area Chart — Mockup
Area Chart Limitations
Stacked area charts have one significant weakness: the middle and upper bands are hard to read accurately because their baseline shifts with each month. The bottom band is easy — it starts from zero. The top bands do not. For precise comparisons between individual series, a multi-line chart or small multiples are better. Use stacked area when the total and relative proportions matter more than exact individual values.
Scatter Plots — Correlation Between Two Measures
A scatter plot places each data point at the intersection of two Measure values — one on the X axis, one on the Y axis. The resulting pattern of dots reveals the relationship between those two measures. A cluster trending from bottom-left to top-right indicates positive correlation. A cluster trending from top-left to bottom-right indicates negative correlation. A cloud with no direction indicates no correlation.
In Superstore, plotting Sales on X and Profit on Y at the Sub-Category level reveals which sub-categories generate both high revenue and high profit — and which generate high revenue but poor or negative profit (the loss-makers hidden inside the total).
Scatter Plot — Labelled Mockup
Adding a Reference Line to a Scatter Plot
A reference line at zero profit divides the scatter plot into a profit zone (above the line) and a loss zone (below). To add it, right-click the Y axis → Add Reference Line → set Value to 0, label to None, and line style to dashed red. Any dots below this line are sub-categories running at a loss — immediately visible without any additional filtering.
Size as a Third Measure
Scatter plots can encode a third Measure by varying the size of each dot. Drag Quantity to the Size channel on the Marks card — dots for high-quantity sub-categories become larger. This produces a bubble chart variant where X position, Y position, and dot size each carry independent information. Keep the size range subtle — very large dots overlap neighbours and obscure the positional pattern the chart is built on.
Area vs Scatter — Choosing the Right Chart
| Scenario | Right chart | Reason |
|---|---|---|
| Total monthly revenue over 3 years with category breakdown | Stacked area | Shows both the total trend and each category's contribution over time |
| Relationship between advertising spend and revenue by market | Scatter | Two independent measures — scatter reveals correlation pattern instantly |
| Single KPI trend over 24 months | Area | Filled area adds visual weight to the volume story — stronger than a plain line |
| Identifying profit outliers across 50 product lines | Scatter | Outliers stand apart from the cluster visually — impossible to spot in a bar chart with 50 bars |
The scatter plot is the most analytically powerful chart in Tableau — and the most underused in business dashboards. The reason is that most business reporting asks "how much?" (bar chart) rather than "do these two things relate?" (scatter). But the scatter reveals something bars never can: outliers. In Superstore, Tables has the fourth-highest Sales of any sub-category but sits below the zero-profit line — a loss-maker hidden inside the total. A bar chart of Sales ranks Tables as a success. The scatter plot exposes it as a problem. Any time your analysis involves two Measures and a set of entities, try a scatter plot before defaulting to bars — you will often find a more interesting story.
Practice Questions
1. After placing Sales on Columns and Profit on Rows, Tableau shows only a single dot. What do you add to the Marks card to produce one dot per Sub-Category?
2. You have a line chart of monthly Sales. What single change converts it into an area chart?
3. A scatter plot already encodes Sales on X and Profit on Y. How do you add Quantity as a third dimension to the same chart?
Quiz
1. A stacked area chart shows three category bands over time. What is the main readability limitation of this chart type?
2. On a Sales vs Profit scatter plot, a dot appears to the right of centre (high Sales) but below the zero-profit reference line. What does this indicate?
3. A scatter plot needs a linear trend line to show the overall relationship between Sales and Profit. Where do you find and add this in Tableau?
Next up — Lesson 23: Histograms and box plots — understanding data distribution and spotting outliers across a full dataset.