Theory
Two numbers, one chart, different scales
Aryan wants one chart showing monthly sales (in thousands) and profit margin (a percentage). But bars sized for 50,000 make a 20% margin invisible, they are on wildly different scales.
BCA105's basic charts (column, line, pie) each show one kind of thing. Real analysis often needs to combine or dissect data in richer ways.
This lesson adds the advanced charts: combo (two scales together), waterfall (how a total is built and eaten away), and radar (many metrics at once). Choosing the right one is still the skill; now you have a bigger toolbox.
At a glance
Advanced chart types
| Chart | Shows | Best for |
|---|---|---|
| Combo | Two chart types + a secondary axis | Sales (bars) + margin % (line) |
| Waterfall | Running total up and down | Profit = income - expenses |
| Radar (spider) | Many metrics on radiating axes | Rating a shop on 5 factors |
| Column/Line/Pie | Compare / trend / share | The basics (BCA105) |
Theory
Combo charts and the secondary axis
A combo chart puts two chart types on one plot, and its power is the secondary axis, a second vertical scale on the right.
Aryan's fix: columns for sales (left axis, 0 to 60,000) and a line for margin % (right axis, 0 to 100%). Now both are clearly visible on their own scales, in one picture. The story 'sales grew but margin shrank' pops out instantly, which two separate charts would never show as clearly.
The secondary axis is exactly what lets two different-scale measures share a chart. Without it, the smaller measure flatlines invisibly.
Quiz
Aryan plots sales (values ~50,000) and margin % (values ~20) on one chart, but the margin line looks flat at zero. What feature fixes this?
- A secondary axis (combo chart), giving margin its own scale on the right
- A pie chart of both values
- Making the chart 3D
- Deleting the sales data
Show the answer
A secondary axis (combo chart), giving margin its own scale on the right
The margin (~20) is dwarfed by sales (~50,000) on a shared scale, so it flatlines. A combo chart with a secondary axis gives the margin its own scale on the right, making both visible together. The secondary axis is the defining feature of a combo chart and the standard solution for plotting two very different scales on one plot.
Think first
Which advanced chart?
Match each to combo, waterfall or radar: (a) how opening balance becomes closing balance through income and expenses; (b) comparing two shops across service, price, variety, cleanliness and speed; (c) revenue and customer-count on one chart.
Show the answer
(a) Waterfall, it shows a running total built up by income and reduced by expenses to reach the closing balance, perfect for financial breakdowns. (b) Radar (spider), many metrics on radiating axes let you compare two shops' whole profiles at once. (c) Combo, two measures on different scales (rupees vs count) share one plot via a secondary axis. Match the chart to the shape of the question, exactly the BCA105 discipline, extended.
Watch out
Where marks leak
Not knowing a combo chart's secondary axis is what lets two different scales coexist. Confusing waterfall (cumulative build-up/reduction to a total) with a plain column chart. And forgetting the BCA105 basics still apply: column/bar = comparison, line = trend, pie = share, and 3D distorts (avoid it). Above all, the rule endures: pick the chart that fits the question's shape. Naming each advanced chart's job earns the marks.
Theory
Charts are the dashboard's face
A combo chart of sales-vs-margin, a waterfall of profit, these are exactly the visuals a manager wants on a one-page dashboard. But building charts by hand for every category is slow. The next big tool, the PivotTable, summarises thousands of rows interactively and feeds charts automatically. That is the centrepiece of this elective, and it is next.
Summary
Key takeaways
- Basic charts (BCA105): column/bar = comparison, line = trend, pie = share.
- Combo chart: two chart types on one plot with a SECONDARY axis, so two different scales coexist.
- Waterfall chart: shows a running total built up and reduced (income minus expenses to a closing balance).
- Radar (spider) chart: compares many metrics at once on radiating axes.
- The secondary axis is the fix for plotting two very different scales together.
- Memory hook: still match the chart to the question's shape; the toolbox is just bigger.