Choosing the Right Chart
Ishaan's first draft for Meera had a pie chart of revenue by category with nine slices, a map of India for the orders from two cities, and a 3D bar chart of weekly on-time rates. Every chart was technically correct, and she could read almost nothing from them. Charts are not decoration; each type is built to show one kind of comparison well.
The rule
Name the comparison first; the chart follows.
Before opening any tool, say what the viewer must compare. Then pick the chart made for that comparison:
| The comparison | Chart | At Weftwise |
|---|---|---|
| Categories against each other | Bar chart, sorted | Revenue by product category |
| Change over time | Line chart | Weekly on-time rate, one line per warehouse |
| How one number is spread | Histogram | How many orders took 1, 2, 3 … days to arrive |
| Whether two numbers move together | Scatter plot | Each product's discount against units sold |
| Two categories crossed | Heatmap | Orders by weekday and hour of day |
| Where, when place matters | Map | Orders by state, to plan a new warehouse |
A few notes that save you from common mistakes:
- A bar is read by its length, so sort the bars and start the axis at zero.
- A histogram looks like a bar chart, but its bars are ranges of one number, such as 0–1 days and 1–2 days, in their natural order. Never sort them by height.
- A map is only worth it when location changes the decision. For "which state orders most?" a sorted bar chart is easier to read, because big states look important on a map whatever their value.
- A pie works only for two or three parts of a whole. With nine slices, the eye cannot compare angles; use a sorted bar instead.
The shortcut
Listen for the key phrase in the question. "Which is biggest" or "by category" → bar. "Over time", "since" or "trend" → line. "How spread out" or "how many took" → histogram. "Does X go with Y" → scatter. "Which day and hour" → heatmap. "Where", and it matters → map.
"Which category earns us the most?"
Categories against each other: a bar chart, sorted from the biggest category to the smallest.
Drills
Answer fast — trust the rule.
"When in the week do customers order most, by weekday and hour?" Which chart?
"Revenue by product category for March." Which chart?
"Daily orders through March, to spot the campaign's effect." Which chart?
"Are orders from the north growing faster than orders from the east?" Which chart fits best?
How should the bars of a histogram of delivery days be ordered?
Remember
- Name the comparison first; the chart follows.
- Key phrases: biggest → bar, over time → line, spread → histogram, together → scatter, day and hour → heatmap, where → map.
- Trap: pies with many slices, and maps where location does not matter.