Data Visualisation - lesson 2 | HackIndia Skills

Key point

One rule

Pick the chart that makes the comparison easiest for a tired viewer. Your recruiter, judge, or teammate should understand the answer in a few seconds.

Do not start with a chart library gallery. Start with the job your chart must do.

Common chart jobs

Most hackathon dashboards need one of four jobs: compare categories, show change over time, show a relationship, or show exact values.

If your chart does not match the job, the data may be correct but the message will still be weak.

Your to-do

Choose by question

Do each one yourself, then tap it to tick it off. The ticks are only a checklist for you: they are not marked or scored.

Use a bar chart to compare categories, like signups by college or bugs by severity.
Use a line chart to show change over time, like daily active users or API latency by day.
Use a scatter plot to show a relationship, like study hours versus quiz score.
Use a table when exact values matter more than shape, like payment status or team member tasks.
Use a single number card only for one important metric, like total donations raised.

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Common mistake

Pie chart trap

Pie charts are often used for category comparison, but they are hard to read when slices are close in size or there are many categories.

For most project dashboards, a sorted bar chart is clearer than a pie chart. It also leaves room for labels.

Tip

Sort for speed

When comparing categories, sort bars from highest to lowest unless the order has meaning. For example, months should stay in calendar order.

Sorting helps the viewer spot the leader, the laggard, and the gap without reading every label.

Example

Chart picker file

Keep a tiny chart decision note in your repo. It shows that your chart choice was intentional, not random.

This is useful in hackathon submissions because judges can see what question your dashboard answers.

dashboard-chart-choice.txt

Project question: Which feature gets the most usage in our campus event app?
Data shape: Categories with counts
Chart chosen: Sorted bar chart
Reason: We need to compare feature usage clearly
Avoided: Pie chart, because 6 slices would be harder to compare
Metric shown: Number of clicks per feature
Viewer action: Decide which feature to improve first

Good defaults

For your first dashboard chart, choose a bar chart or line chart. They handle most project questions well and are easy to label.

Use fancier charts only when they solve a real problem. A recruiter-ready dashboard is clear before it is stylish.