Rows: one thing, one line

By the end of this lesson you can point to a row in a table and say what one "thing" it describes.

Why it matters

Before you can count anything in a table, you must know what each line stands for. If one line is one sale, then counting lines counts sales. Get this wrong, and every answer after it is wrong too.

The idea in plain words

Think of a class register. Each line is one pupil. Everything on that line is about that one pupil: their name, their age, whether they came today. You would never write two pupils on one line.

A table works the same way. Each line across is about one thing. That line is called a row.

Row: one line across a table. Everything in a row is about the same one thing.

In Amara's table, the "one thing" is one sale. A sale is one customer buying one kind of fruit. So:

• one row = one sale,
• 9 rows = 9 sales,
• a new sale = a new row.

Watch the teal row: everything on that line is about one sale. (The picture also shows a column and a cell. Those come in the next two lessons.)

See it done

Question: how many sales did Amara make on Tuesday?

Data: Amara's week of sales, market-stall-week.csv. It is made up for this course (synthetic), so you can practise on it freely.

1. Decide what one row is. In this table one row is one sale.
2. Find the Tuesday rows. Look down the day list for Tue. In a spreadsheet every row has a number down the left side. The Tuesday rows sit together, from sheet row 12 to sheet row 20.
3. Count the rows. Count every line from S011 down to S019: S011, S012, S013, S014, S015, S016, S017, S018, S019. That is 9 rows.
4. Turn rows back into the thing. 9 rows, and one row is one sale. So Amara made 9 sales on Tuesday.

Nine rows on Tuesday means nine sales on Tuesday.

Tip: there is a quicker way to count. Row 20 minus row 12 is 8, then add 1 because you count both ends: 8 + 1 = 9. You will learn a formula that counts for you in Module 3.

Notice something. Amara made 9 sales, but she sold more than 9 fruits. Row S011 alone is 6 bananas. Counting rows counts sales, not fruits. Keep that in your pocket. It comes back later.

Your turn, with help

Look at the picture of the nine Tuesday rows again.

1. How many of the Tuesday rows are for Pawpaw?
2. So how many Tuesday sales were sales of pawpaw?

Hint: run your finger down the fruit column, and only count the lines that say Pawpaw.

Show the answer

1. 2 rows: S013 and S015.
2. 2 sales. One row is one sale.

Your turn, alone

Use the picture of the nine Tuesday rows.

1. How many Tuesday rows are for Banana?
2. What is the one thing that row S016 describes? Say it in a sentence.
3. Lucía, a teacher in Bogotá, makes a table of her class. Each row is one pupil. She has 15 rows. How many pupils are in her table?
4. Amara sells 2 more watermelons to a new customer on Tuesday evening. How many Tuesday rows will there be now?

Check your answers

1. 2 rows (S011 and S017).
2. One sale: on Tuesday a customer bought 2 watermelons.
3. 15 pupils.
4. 10 rows. A new sale is a new row, even if it is the same fruit as an earlier sale.

Watch out

• Counting rows when you meant to count items. 9 rows is 9 sales, not 9 fruits. Ask: "what is one row?" before you count.
• Counting the heading line. The top line holds the column names. It is not a sale. Do not count it.
• Two things squashed into one row. If one row said "6 bananas and 3 pineapples", it would hide a sale. One row, one thing.

Say it back

1. What is a row?
2. In Amara's table, what is one row?
3. A table has 25 rows of data, and each row is one hospital visit. How many visits?

Show the answers

1. One line across a table, all about one thing.
2. One sale.
3. 25 visits.

What is next

Each row holds several facts: a time, a fruit, a number. Why are they lined up in neat columns, and why do data people call them "variables"? Next lesson.