12 Data Visualization¶

The chart is made up of several building components, including the data itself, which is shown by lines and dots, several text elements above and below the chart, text elements incorporated into the chart, and supporting chart elements like axes and gridlines.

• Use a grid to position and size elements.
• Place the chart title in the top left. Least important info goes in the bottom right.
• Align axis labels meaningfully both horizontally and vertically.
• Avoid visible frames, use an invisible grid and boxes when you embed it.
• Use Break the grid technique to highlight specific data points or outliers.
• For multiple visualizations, follow the reading sequence from top-left to bottom-right.

Creating a visual hierarchy which guides the reader on what to look at first, what to look at next, and what to look at last. you may make specific aspects in a publication or visualisation stand out more. With regard to that,

• Position element in the x and y dimensions.
• Layering elements on top of each other in the z dimension
• Adjust the size of elements for emphasis.
• Use colors effectively.
• Highlight elements by enclosing them.

Certain chart types tend to grow to a wide layout, while others will quickly evolve to a tall layout. such as vertical bar charts often have a greater width than height, unless they display a limited number of values. Horizontal bar charts often have a taller than broad appearance and rise vertically. Thus,

• Choose a chart type that best fits the data and message.
• Use the "banking to 45 degrees" rule for line charts to account for aspect ratio differences.
• Scale up data marks and font sizes for larger charts; use thicker lines, larger dots, and bigger letters. For smaller charts, scale them down.
• Bigger charts can hold more data, so adapt by including or excluding data based on chart size.

Your visualisations will be more readable if you round the numbers. Round numbers are simpler to read and may often be presented more effectively without compromising precision.

• Use words like million or billion instead of many zeros.
• Apply SI prefixes (e.g., "k" for thousands, "M" for millions).
• Use scientific notation, such as 1.3e+6 for 1.3 million.
• Include signs ("+", "-") to indicate growth.
• Add units and symbols for values and currencies.
• Limit date axis labels to 5-10; label every 2-5 years for spans over a decade.
• Format year labels as (“2018”, “2019”) instead of (“2018/01/01”, “2019/01/01”).
• Adjust label formatting to avoid overlaps, using abbreviations (e.g., "Jan", "Feb") and shortened years (’18, ‘19) for narrow charts.
• Use the ISO 8601 standard (YYYY-MM-DD) for dates.

The fact that tables are far more useful than visualisations for looking up numbers across several dimensions is a popular argument for publishing data as a table. Tables must also be quickly scannable to facilitate effective value searching. This affects their design in a few ways.

• Use colors to aid in looking up values, not to distract.
• Align text values left in columns.
• Align numbers right in columns.
• Ensure consistent formatting of numbers within a column, including rounding and significant digits.
• Adjust column widths to fit the data.
• Balance vertical spacing between text in each row with enough whitespace.
• Place the main lookup column (text or number) as the first column of the table.