Graphs

Visualising Data: Week 5

Lecture Notes

Data Presentation Styles: Why use Graphs?

  • Why do we use graphs?
    • Graphs help to make comparisons easier.
  • Often designers choose a style of graph that is trendy, rather than the graph best suited to the data you’re trying to present.
  • The human brain gravitates towards comparing the width or height of shapes in graphs, and its usually easy to underestimate the difference in surface area when looking at a bubble chart for instance. Bar graphs are much easier to draw comparisons from because we only have to consider the length as a variable. Consider which graph type is easiest to analyse and compare differences with.
  • Using circles in graphs always leads the audience to underestimate the size difference.
Cairo, A. (2013). The Functional Art. Berkeley, California: New Riders.
  • Three graph types commonly used
    • Time series chart (data over time)
    • Bar chart (one variable)
    • Scatter plot (one variable on each axis)
    • Pie chart (comparing proportions)

Visualising Data: Week 1

Lecture Notes

What is Data Vis?

  • Data: Values of qualitative or quantitative variables belonging to a set of items.
  • Data are typically the results of measurements and can be visualised using graphs or images.
  • Data alone carries no meaning. Data must be interpreted and take on a meaning before it becomes information.
  • Data Visualisation: The visualisation of data. Viewed by many disciplines as a modern equivalent of visual communication. Involves the creation and study of the visual representation of data.

[Data visualisation is] information that has been abstracted in some schematic form, including attributes or variables for the units of information.

Michael Friendly (2008). “Milestones in the history of thematic cartography, statistical graphics, and data visualization.” As cited in DataVis POD01 – What is Data Vis?
  • A primary goal of data visualisation is to communicate information clearly and efficiently using statistical graphics, plots, and information graphics.

What is the difference between information graphics and data visualisation?

  • Not all information visualisations are based on data, but all data visualisations are information visualisations.
  • To be a data visualisation, there should be quantitative values on the axis.
  • Effective visualisation helps users analyse and reason about data and evidence. It makes complex data more accessible, understandable and usable.
  • Bar graphs are arguably the best form of data visualisation if you have two variables to communicate.
  • If you’re looking at data over time, a line graph is the best choice for visualising the data.
  • Bar charts, line graphs and timelines are easy to recognise, read and understand as the audience is familiar with them.