lesson
Updated 6 days ago · 2 views
If a fitness app tracked your heart rate during a sprint using a pie chart, you would end up with a chaotic wheel with fifty tiny slices. Choosing the wrong graph turns clear measurements into visual nonsense.
To pick the right display every time, you only need to answer two questions: what type of data do you have, and what purpose should the visual serve?
Step 1: Identify Your Data Type
Before drawing anything, check whether your information consists of descriptive groups or measurable quantities. Categorical data sorts items into descriptive labels, while numerical data represents values you can count or measure.
📊Interactive diagram
Categorical data splits into nominal (labels without an inherent order, like shoe brands) and ordinal (categories with a meaningful rank, like race places: 1st, 2nd, 3rd).
Numerical data splits into discrete (distinct countable values, like number of pets) and continuous (measurements that can take any value along an interval, like height in centimeters).
Once you know whether your data is labels or numbers, how do you match it to the right visual tool?
Step 2: Match to the Display Purpose
Every graph has a specific mathematical job. Scottish engineer William Playfair invented the bar chart, pie chart, and line graph in the late 1700s because the human brain interprets shapes and angles far faster than rows of raw numbers.
📊Interactive diagram
Use a bar chart to compare separate categories, or a pie chart if you want to emphasize how individual categories contribute to a 100% total.
Use a line graph when a single numerical variable changes continuously across time, a histogram or box plot to explore the shape and spread of a single continuous variable, and a scatter plot to see if two numerical variables share a relationship.