Data visualisation

Why is data visualisation important?

• Create summaries for data

• Create charts for interpretation, analysis + learn from data

• Useful in identifying data errors/extreme value

• Essential in communicating messages

Why tables

• associations within table → average between two groups f.e

• to look up specific numbers

• precision is needed to make comparison between diff values

  • v important

  • numbers don’t lie

• values being displayed have different units and magnitudes

Why graph

• patterned based → less about individual values

• visualise pattern trends and development and associations

What are pre-attentive attributes

• are characteristics that can be used in a graph for easier interpretation

• characteristics are already registered → not much cognitive effort

• Colour

• size the size doesn’t correlate to number

  • bubble charts

• length is most effective

  • bar f.e: have a certain length, able to compare magnitudes

  • number does correlate to the length

• shape

• Minimise eye travel

  • make it look visually pleasing

• Data ink ratio

• interested in development only

• horizontal lines can be removed unless you want to emphasise it

Points

• scatter charts

  • important aspect: what does each row represent

    • each row is turned into a point

• graphical representation of the relationship between two quantitative variables

• Avoid 3D and many slices in pie charts

Data ink ratio

• ink is used to create a graph

• related to amount of data ink

  • the ink is used is important to convey the message

• useless ink: not related to data itself

• how to increase data ink ratio:

  • remove the lines in tables → as it doesn’t improved the table

• ink is used to create a graph

• related to amount of data ink

  • the ink is used is important to convey the message

• useless ink: not related to data itself

• how to increase data ink ratio:

  • remove the lines in tables → as it doesn’t improved the table

Points

• scatter charts

  • important aspect: what does each row represent

    • each row is turned into a point

• graphical representation of the relationship between two quantitative variables

Line charts

• when to use it?: used to see developments overtime

• interval variable: series of consecutive categories, continuous

• no data

  • shouldn’t do, remove the months or draw a line, keep the months and make clear that there isn’t a data

Bar chart

• emphasise individual values

• suited to compare categorical variables

• vs column charts (what is this

• horizontal vs vertically → what is more visually pleasing

Stacked column chart

Clustered column chart

Clustered bar chart

100% stacked bar chart

Stacked bar chart

Waterfall chart

Bar vs Column charts

• horizontal versus vertical

• Often more pleasing to the eye, especially when text labels are long

• And when there are many bars to compare

Dual axis chart

Does a line chart need to start a 0?

• yes always

• unless there is a reason not too

  • when?: range of measurement is small, negative values

Boxplot

• method for graphically depicting numerical data through quartiles

• provide visual representation of the spread of the data based on quartiles

• indicates central tendency and variability using five summary statistics (the median, two hinges and two ‘whiskers’), and all "outlying" points individually

• bar in the middle of the box is median → arranged according to magnitude, not the mean

• the distance between the upper and lower hinge is the IQR range

• if there are no values that more than 1.5 times the IQR range from the hinge = no outliers will be present and dependent on the distribution of the variable

• Boxplots take up less space than Histograms

• tells how the data is spread out

• useful when comparing distributions between many groups

• for easier visual understanding turn it 90 degrees

Pie charts

• Avoid pie charts to properly compare categorical data

• inferior to bar for comparing data

Decluttering

• the process of increasing the data-ink ratio

• irrelevant data is removed or process to increase data ink ration

• Focus is vital

Choropleths

• A choropleth map is a geographic visualization that uses different shades colours, or symbols to indicate the values of a quantitative or categorical variable associated with a geographic region or area

• Choros (area) and plethos (value)

Problems

• Area bias

Solution

• Group data

Cartograms

• uses geographic positioning but purposefully represents map regions that do not necessarily correspond to land area