Overview

Teaching: 5 min
Exercises: 5 min

Questions

• What are data variables and categories?

• What are data values and replicates?

• What is the difference between absolute and relative values?

Objectives

• To identify data structure features in Gapminder data

• To be familiar with differentiating data structures for choosing a good chart

Data Organization Challenge

What years are represented in the Gapminder data?

Answer

1952-2007

Which variable is more appropriate to group by? Why?

A. country
B. gdpPercap

Answer

A. country, because it is a ‘categorical’ variable

Key Points

• ‘Variables’ are associated with columns in tidy data.

• As a descriptor of a specific column of data, ‘variables’ tend to describe numerically continuous data, while ‘categories’ describe discrete or categorical data that is organized in groups.

• ‘Values’ are associated with cells in a data table.

• ‘Replicates’ are values with similar variables and categories most often seen in experimental data.

• ‘Absolute’ values receive context by their units, while ‘relative’ values are standardized in some fashion (i.e., proportion, per unit) for comparison among categories.

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