DATA JOURNALISM TRAINING

Day 3

FROM DATA TO

DIAGRAMS

Mental model

2+2 = ?

Mental model

Process data

How many 7 do you see?

1 4 6 7 4 3 6 7 9 9 5 3

7 5 1 7 8 9 4 3 0 7 1 2

3 4 7 8 1 0 6 4 2 7 1 7

2 4 5 1 1 7 8 6 7 2 0 1

Process data

How many 7 you see:

1 4 6 7 4 3 6 7 9 9 5 3

7 5 1 4 7 8 9 4 3 0 7 1

3 4 7 8 1 0 6 4 2 7 1 7

2 4 5 1 1 7 8 6 7 2 0 1

Process data

How many 7 you see:

1 4 6 7 4 3 6 7 9 9 5 3

7 5 1 4 7 8 9 4 3 0 7 1

3 4 7 8 1 0 6 4 2 7 1 7

2 4 5 1 1 7 8 6 7 2 0 1

Form follows function

Before editing data into a visualisation, think of the questions readers

may have, and the Journalistic stories you want to tell.

Your visualisation should then answer the readers' questions

We want to Presentation chosen

Show part of a whole Pie chart

Compare values from different categories Bar chart

Follow value over time (timeseries) Line graph

Show interaction between 2 values Scatterplot

Show data related to geography Map

Data presentation “rule of thumb”

Pie charts

When to use

● To compare part of a whole at a given point in time

● Best for three to six categories

When not to use

● For any data which does not add up to 100% (i.e. part-whole)

● When there are more than six components

● When the values of each component are similar

● When you want to convey exact values

Pie charts

Tips

● Works best for categorical data

● Limit number of pieces

● When drawing a pie chart, ensure that segments are ordered

clockwise by size

● Labelling the segments can communicate the data more

effectively

● Do not try and compare multiple pie charts – use another

Bar (column) charts

When to use

● To compare different

groups or categories

● To track changes over

time

● Horizontal bar charts are

more suitable when we

have many items to

compare.

When not to use

● Do not use it for larger

data sets: use line charts

instead

Bar (column) charts

● Don’t overload; although you can do multiple colours and pack two categories in

there, if it’s too many categories it becomes confusing.

● Always label your axes whoever is looking at your graphs needs to know what the

units are they are looking at.

● Start your values at 0. Most spreadsheet tools will automatically adjust the range:

undo this and set it to 0 – this shows contrast in an appropriate scale! We’ll show

you why this is important in the next module.

● Sort values. It is advised to have your bars sorted according to their lengths,

unless there is a certain order for the items you are comparing that you do not

want to change.

Line charts

When to use● To track changes over

time

● Can depict multiple series

● To display more numerous data

When not to use● If the x-axis has non-

numeric values

● When you want to show a part-whole relationship

Line charts

● Line graphs are ideal for continuous data

● On the y axis we still have our values on the x axis we

have the time measured.

● This graph works best if the time interval between the

measurements is equal (Of course line charts are not

limited to time series).

● Again it’s important, when comparing multiple

categories, to start your y axis with 0.

Bubble charts

Flaws of bubble charts (borrowed from Alberto Cairo)

Flaws of bubble charts (borrowed from Alberto Cairo)

Text

http://www.wordle.net/

Telling a Story

Tell readers why they should care about your

visualisation

Tell readers why they should care about your

visualisation

Design guidelines

● Use color wisely: http://colorbrewer2.com

http://www.colourlovers.com/

● Keep a consistent style

● Choose one highlight

● Remove junk!

http://darkhorseanalytics.com/blog/