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Combo Charts

Combo charts combine two chart types – typically bars and a line – in a single visual. They're useful when you want to compare two related metrics that have different scales or units.

Combo charts are perfect when one measure might relate to the other. For example: "When discounts are higher, do sales go up?"

When to Use Combo Charts

Comparing volume (bars) against a rate or percentage (line)
Showing sales quantity alongside average discount
Displaying revenue with profit margin trend
Any time two metrics tell a better story together

Tips for Effective Combo Charts

Use bars for the "main" metric and lines for the supporting metric
Make sure the two metrics are actually related
Don't overload – two measures is usually the sweet spot
Consider using different colors to clearly distinguish the bar from the line

Combo charts can get confusing if the two metrics aren't related. If viewers have to think hard about the connection, consider using two separate charts instead.

Assignment

On your "Trends" page, insert a "Line and clustered column chart" spanning the bottom half.
Configure the chart to show:
- The sum of sale_quantity as the column's Y-axis
- The average sale_discount as the line Y-axis. You'll need to use the dropdown to change from Sum to Average.
- The date_week (i.e., the week of the year) as the X-axis.
Format the title: General → Title → Text → "Sales vs Avg Discount"

Notice that on days where the discount is higher, there tend to be more sales... interesting.

Save the project and, from the course directory, submit the CLI tests.