Thirty numbers or one picture?
The school office checks how many students came in each day. One way is a long list of numbers. Another way is five bars on a screen, one for each day.
Which one tells you in one second that Friday is the worst day? The bars. This lesson is about the different ways to show numbers so a person understands them fast.
Key words
| Word | What it means | Example |
|---|---|---|
| Data visualisation | Showing data as a picture, so people see it fast. | A bar chart |
| Graph | A picture with two lines called axes. It shows how one number changes with another. | Temperature through the day |
| Chart | A picture that shows amounts or parts, often with bars or slices. | A pie chart of lunch choices |
| Table | Rows and columns of facts. You read the exact numbers. | A bus timetable |
| Report | A document that explains data in words, tables and pictures. | A monthly sales report |
| Dashboard | One screen with several small pictures. It updates often. | A screen in the school office |
| Infographic | A poster that mixes pictures, big numbers and a few words. | A poster about healthy eating |
| Axis | One of the two lines of a graph. Each one has a label. | Days along the bottom |
The cells students fill in are left blank in this preview.
Six ways to show data
| Format | What it is | Use it when |
|---|---|---|
| Graph | Two axes. A line or dots show a change. | You want to see a change over time. |
| Chart | Bars, slices or blocks. | You want to compare amounts or parts. |
| Table | Rows and columns of exact numbers. | People need the exact value. |
| Report | Words, tables and pictures in one document. | You must explain and give the reasons. |
| Dashboard | Many small pictures on one live screen. | People check the numbers every day. |
| Infographic | A poster with pictures and big numbers. | You want to tell the public a simple story. |
The cells students fill in are left blank in this preview.
Graph or chart?
People often confuse these two words. Here is a simple rule.
A graph has two axes and shows how one thing changes with another. A line going up and down over a week is a graph.
A chart shows amounts or parts. A set of bars, or a round pie cut into slices, is a chart. Many people say "graph" for both. Ask your teacher which word your exam uses.
Try it: a chart made of hashes
days = {"Mon": 28, "Tue": 30, "Wed": 27, "Thu": 25, "Fri": 18}
for day in days:
bar = ""
for count in range(days[day] // 2):
bar = bar + "#"
print(day, bar, days[day])
# The // sign divides and drops the decimals: 28 // 2 is 14.
# Each # is 2 students. Change a number and press Run again.
Always add labels
data-callouts.tip.label
A picture with no title and no labels is only a nice picture. Nobody can read it. Say what the bars are, what the numbers mean and what the unit is: students, pounds or minutes.
Dashboard or report?
A dashboard is for a quick look. A manager sees today's numbers in five seconds. The numbers change by themselves.
A report is for a slow read. It is written once and says what happened and why. A dashboard shows the problem. A report explains it.