5.2 Visualising and Interpreting Data

5.2 Visualising and Interpreting Data

So far we have learnt how to read and make pictographs, bar graphs, clustered-bar graphs, and dot plots. We now examine some more ways of visualising data.

Line Graphs — Temperature

The following figure is a clustered-column graph^? that shows the monthly maximum temperature in Kerala and Punjab in 2023.

Now observe the following line graph^? for the same data. Do both graphs represent the same information?

We call such a graph made up of lines a line graph. Line graphs are generally used to visualise data across time.

Step 1: Identifying the given information

Notice how the graph is organised, what scale is used, and what patterns the data shows:

• The data for each month for a city is marked and connected by lines to show the change over time. Kerala's data is shown using blue circle marks connected by blue lines and Punjab's data is shown in red.
• The horizontal line shows the months of the year. The vertical line shows the temperature in °C.

Step 2: Inferring from what is given

Analyse and interpret each of the observations you made. Share appropriate summary/conclusion statements:

• In Punjab, the monthly maximum temperature increases from January to June, reaching a high of 38°C. Then, it reduces to just under 35°C in July, stays mostly flat till September, and then falls continuously till December, reaching about 23°C. January has the lowest among the monthly maximum temperature values — of about 19°C.
• Kerala's trend is different — it stays mostly flat throughout the year. The peak is around 33°C in April and the lowest point is around 29°C in July. Notice that the monthly maximum temperatures in Kerala are similar both in summer and winter.
• In short, the temperature in Punjab varies more, reaching colder and warmer temperatures than in Kerala. On average, it is hotter!

This can trigger questions in different directions, some of which can be answered using the data. Are some directions to think about:

• Why are the trends so distinct in these two states?
• What factors determine a region's temperature?
• You might be curious to look at the trends of a few other states. Are there other types of trends that states exhibit?
• Which states show trends similar to Punjab's? Is there anything common between these states?
• What would a plot of the monthly minimum temperatures for these states look like?

Space Jam: A Traffic Problem in the Sky

Take a look at the line graph below showing the annual number of objects launched into space. This data plots the number of objects launched into Earth's orbit from 2012 to 2023.

Step 1: The horizontal axis shows the year (2012–2023); the vertical axis shows the count of launches. Separate lines are drawn for the world, the USA, and China.

Step 2 — Inferences:

• In 2024, the worldwide count is around 2800, whereas in 2023, it was around 2900. We can say that 2023 saw the highest number of objects launched into space worldwide (assuming the trend before 2012 was decreasing).
• The counts of the three countries don't add up to the worldwide count. Therefore, we can infer that the counts of other countries are not shown in this visualisation.
• For the USA, the increase from 2022 to 2023 is more than that from 2023 to 2024. We can say this by looking at how steep the line segments are — the steeper the line, the greater the increase.

Which of the following statements are valid inferences from the graph?

• From 2012 till 2024, the worldwide count of space object launches increased every year. ✓
• USA is a major contributor in the years 2022–24, launching about ⅓ of the worldwide count. ✓
• Nepal did not launch any object in the period 2012–24. Cannot conclude from this graph — Nepal's data isn't shown.
• The combined count of object launches by China and Russia in 2024 is about 400. Cannot conclude — Russia's line isn't shown.

Catch the Pattern in Rain

The following graphs show monthly average rainfall data of a few cities — Kovalam (Kerala), Udupi (Karnataka) and Mumbai (Maharashtra) on the West Coast; and Rameswaram, Chennai and Puri on the East Coast.

The data shows the monthly average rainfall in 6 cities. This means rainfall data is collected over a few years in every city. The total rainfall in a month, say June, across years is averaged to get the monthly average rainfall in June in a city.

Mark three cities on a map of India. What is common to how they are grouped in the graphs? Share your observations and inferences:

• Kovalam, Udupi and Mumbai are along the West Coast. It appears that these regions along the west coast have similar rainfall patterns.
• Identify the peak months and low months of rainfall for each city. Udupi, Mumbai and Kovalam see most of its rain during October–December; Chennai starts getting rain from June onwards, peaks at around October–December. Puri, on the east coast, continues till December. Rameswaram receives very little rain from January–September.
• Read about the south-west monsoon and north-east monsoon and which regions come under the influence of these winds.

Infographics

In Grade 6, we saw an example of how infographics can be used to communicate information and insights more clearly and quickly in a visually appealing way. Take a look at the following infographic idea: "Wheat vs Rice" — a map of India showing state-wise preference between wheat and rice on a colour scale from −100 (mostly wheat) through 0 (both equal) to +100 (mostly rice).

This infographic^? compares the preference between rice and wheat in different states. The colour scale at the top right indicates how to interpret the different shades in terms of preferences. The difference between the two captures how much of a state's population eats wheat or rice. A value of −100 doesn't mean that the state doesn't consume wheat at all. It means that this state prefers mostly rice and the difference between wheat consumption and rice consumption is the highest.

What Can a Strip Say?

Manoj has an interesting hobby. He makes note of what he does throughout the day. He records his activities by colouring a strip of paper with 48 boxes, marking time in 30 minute intervals from midnight to midnight. He has recorded five types of activities for three different days of the week (e.g. Wed, Sat, Sun) using coloured strips, shown to the right: (i) Sleeping (ii) Eating (iii) Meeting friends, hobbies, media, time with family (iv) Attending classes, studying and homework (v) Showering and getting dressed, yoga or exercise (vi) Travelling.

Look at the three coloured strips carefully:

• (i) What activity does each colour stand for?
• (ii) The three strips correspond to the days Friday–Sunday in some order. Which day do you think each strip represents?
• (iii) On one of these days, he went out with friends to watch a long movie. When do you think this happened?
• (iv) At what time does his school break for lunch?
• (v) What more can the strips tell us?

Data Story: Sleepy-Deepy

Do you remember the sleep time pie chart from the Proportionality chapter? Isn't it amazing that there are animals that sleep as little as 2 hours per day and animals that sleep as much as 20 hours per day? How about insects — have you seen any insect sleep? Humans typically sleep for about 7–9 hours a day. The sleep duration can vary greatly among people. The amount of sleep people need depends on age, living conditions, lifestyle (food they consume, the activities they engage in, etc.) among other factors. You may have observed that babies sleep longer than adults.

The line graphs below show typical sleep durations of Indians across ages 6 to 75. The second picture is a zoomed-in version of the first picture. Unlike the earlier graphs that were made up of a few connected line segments, this line graph looks like a smooth curve because it contains 80 data points that are placed very close to each other, making a smooth curve of 70 columns.