Rainfall, infographics and strips

Start again with where the numbers come from. 'Monthly average rainfall' means rainfall in a city was recorded over several years, and, for example, the June totals of all those years were averaged to give the June figure. So one unusual monsoon does not spoil it.

The book plots six cities. Kovalam, Udupi and Mumbai are on the west coast. Rameswaram, Chennai and Puri are on the east coast. Put them on a map and you see the grouping is by geography, and the west coast clearly gets more rain.

The timing is different too, and that is the interesting part. Udupi, Mumbai and Kovalam get their peak rain in June–August. Rameswaram gets most of its rain in October–December, at the other end of the year.

Chennai starts getting rain from June, peaks in November and carries on into December. Puri, though it is on the east coast, peaks in July–September, more like the west. January–March are dry everywhere, and Rameswaram gets very little rain from January all the way to September.

These two patterns have names: the south-west monsoon and the north-east monsoon. A graph has led you to a question that geography answers.

Data can be shown in other ways too. An infographic gives information quickly and attractively. One in the book is a map showing the difference between how much rice and how much wheat people eat (per person) in each state, on a scale from −100 to +100.

Read the scale carefully. +100 does not mean a state eats no wheat. It means the state prefers rice and has the largest difference between the two. Confusing a difference with a total is the easiest way to misread an infographic. The map shows a striking split across the country.

Last, Manoj's strips. He colours a strip of 48 boxes, one for every 30 minutes from midnight to midnight, to show sleeping, eating, friends and hobbies, classes and study, washing and exercise, and travelling. With three strips for three days you can tell which day is which, when the school lunch break is, and when he went out to a long film. A whole day in 48 coloured squares.