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A Glossary of Visual Types

This sections show and names several common chart types.

Bar and column charts

Bar charts have horizontal bars, column charts have vertical columns.

Bar charts are considered boring but are easy for readers to understand.

chart

This is the very first bar chart ever recorded, also by William Playfair in about 1780.

chart_bar_playfair

Bar and column charts can be stacked or clustered (side-by-side). It is best to only two or three at most items.

An example stacked column chart.

chart

An example clustered column chart.

chart

Line Chart

Line charts usually have dates on the x-axis and show progress over time.

This is the very first line chart ever recorded, also by William Playfair in about 1780.

chart_line_playfair

This line chart shows the seasonal nature of bike hire volumes over several years.

chart_line_time_series

This line charts suffers from having too many lines of different colours.

chart_line_many

This line chart is used for emphasis - to show that London is an outlier to the other UK regions.

chart_line_emphasis

Pie Charts

Pie charts show composition (parts in a whole). They are very popular but are scorned by data visualisation experts. Have a look at the chart below and see if you can understand why.

chart_pie_dental

Source: An overview of adult dental fee exemptions in NHS primary dental care in England

Scatter Plot

This scatter plot shows the relationship between sales and profits for ceratin types of drinks.

chart_scatter

Card

Cards highlight important numbers. They are often placed at the top of the dashboard to show the critical numbers for the organisation.

chart_card

Bubble Map

Bubble maps (also known as circle or point maps) are most useful where the location is a specific location.

chart_bubble_denmark

The chart below shows the number of jobs in each UK region split into three categories. Does it succeed?

chart_bubble_uk

Shape Map

Shape maps (also known as choropleth maps) are useful where we want to show the size and boundaries of an area.

This area map shows the level of deprivation in London. Dark blue areas have the most deprivation and yellow the least.

chart_map_shape_london_imd

However they can be misleading, by equating area with a variable. The three maps below show, for each of the 32 London borough, the percentage of people in work who were born either in the EU (named EEA, pre-Brexit data but excludes the UK), the UK, or the rest of the world (named Other). In what way could these maps be misleading?

chart_map_shape_london

Tables with conditional formatting

Conditional formatting of the values in a table can make the table easier to read and understand. There are a few types of conditional formatting:

data bars
background colours
sparklines (tiny line or column charts next to a value to show the trend)

Example: data bars

Data bars helps us to see quickly which numbers are largest, which are negligible, and to spot anomalies.

chart_table_databars

Example: background colours

This Risk and Controls Self Assessment (RCSA) uses background colours to show the severiry of the risk.

chart_table_rcsa

Example: sparklines

Sparklines provide context to the current value by giving us the gist, but not the detail, of the time-series history.

chart_table_sparklines

Small mutiple charts

Small multiple charts can be very useful. Instead of a single complex chart, it may be easier to show several smaller simpler charts.

Small Multiples of bar charts

chart_trellis_bar

Small multiples of scatter charts

chart_trellis_scatter

Small multiples of line chart (with free y axis)

chart_trellis_line

Other Visualiation Types (use with care!)

100% stacked bar chart

100% stacked bar chart emphasise the ratios / percentages but not the absolute values

chart_stacked_bar_football

chart_stacked_bar_jobs

Bullet Chart

The bullet chart is a specialised bar chart typically to compare actual - reference - target

Examples

actuals this year - actuals last year - budget this year Risk
exposure today - risk exposure yesterday - limit

chart_bullet

Dual axis bar and line chart

A dual axis chart compares two variables, usually over a common date/time axis. They can be useful in spotting relationships between the two variables. However, A reader must take more time and effort to understand a dual axis chart.

chart_dual_axis

Ribbon chart

A ribbon chart is a variation of a stacked column chart but orders the legend items (colours) so that the biggest item in each x-axis category is at the top of the stack.

chart_ribbon