How to determine what chart type to use

There are a lot of options when it comes to presenting data in a chart or graph format. You should make this determination based on:

• what type of data you need to convey; and
• the users you are conveying the information to.

There is no shortage of options when it comes to presenting data in a chart or graph. This guidance outlines:

• the most frequently used types of charts and graphs;
• instances when you might use them; and 
• best practices for using them.

Bar and column charts

Bar charts have horizontal bars and column charts have vertical bars. Use these types of charts when you want to:

• compare different values from multiple categories; or
• show significant differences over time.

There are 3 types of bar charts

1. Single bar charts. Use this when you want to know the quantity, ratio and frequency of each category.
2. Clustered bar charts. Use this to compare items across categories.
3. Stacked bar charts. Use this to show part-to-whole relationships among each category.

Best practices for creating bar and column charts

• Always start the y-axis at 0.
• Use a horizontal bar when you have long labels.
• Order by data series unless you are working with dates.
• Use contrasting colours for greater clarity when using stacked column charts.

Line charts

Use a line chart when you want to:

• compare values or show a trend over a period of time;
• display large or small changes;
• compare changes to more than 1 group of data; or
• show a particular correlation.

Best practices for creating line charts

• Avoid comparing more than 5 to 7 lines.
• Ensure the colours you choose provide enough contrast.

If you are not comparing value over time, you should select a bar graph.

Pie charts

Use these chart types when you want to:

• show parts of a whole;
• represent numbers in percentages; or
• display the composition of something.

Do not use this chart type:

• to display things like changes over time; or
• for values that are very similar. Use a bar chart in these instances.

Best practices for creating pie charts

• Use pie charts only if you have maximum 6 categories.
• The total sum of all segments needs to equal 100%.
• Order slices according to their size for easier comparison.

Scatter charts

Use scatter charts when you want to show:

• relationships between 2+ variables;
• values of individual data points;
• patterns in the data; or 
• gaps in the data

Best practices for creating scatter charts

• Randomly sample a subset of data points if the number of data points you have will make it hard for users to see relationships between points and variables.
• Add a trend line if your chart displays predictive or correlational relationships between variables. This will help uses understand how strong the relationship is.
• Help users see how data points are grouped together by giving each point a distinct colour or hue.
• if you are presenting insights, you can also use colour or annotations to highlight particular points of interest.