In the process of Data Visualisation, once the data and business question are finalised, the next step is to decide on the visualisation.
Graphs and charts reduces huge amount of information into simple and easy-to-understand formats.
The purpose of the graphics (Graphs n Charts) on dashboard is to transform data and bring alive the underlying story whether it is to show a comparison, a relationship, or highlight a trend.
The challenge now is to choose the right graph or chart from the variety of options available. But before, establishing the reasons for data presentation aids in choosing the right graph/chart for visualisation.
The four identified categories for data presentation are -
- Comparison
- Composition
- Distribution
- Relationship/Trend
This blog covers an overview of most frequently used charts. (The list by no means is all-inclusive). And the rest is up to one’s own imagination.
1. Bar charts are ideal for information comparison and uses either horizontal or vertical bars (column chart) to show numerical comparison. The bars represent different categories of data. The length of each bar represents its value.
When to use — To compare data across categories.
Bar Chart Visual -
2. Line charts reveal trends or progress over a period of time. It is a good way to visualise continuous data set or a sequence of values. Best suited for trend based data and analysing the rate of change over a period of time.
Values are plotted on line chart and the data points are connected to show a trend. Multiple trends can be highlighted and compared by plotting lines of different colours.
When to use — To compare data across categories.
Line Chart Visual -
3. Pie charts are used to show a data composition, typically for representing numbers as proportions or percentages of information — A part to whole. The sum total of all proportions being 100%.
When to use — To Show proportions/percentage
Pie Chart Visual -
4. Scatter plots are mostly used in correlation and distribution analysis. This is a type of graph that helps to determine if relationship between two variables exists or not. An effective visual tool to show trends, concentrations and outliers in distribution of data.
When to use — To investigate the relationship between different variables.
Scatter Plot Visual — Cool Drinks Sales on a sunny day
5. Heat maps are used mostly for information comparison. It provides a level of activity or a rating information (e.g High to Low, Strongest to Weakest, Excellent to Poor), all displayed using different colours.
When to use — To show the relationship between two factors.
Heat Map Visual -
6. Histogram chart is used to see how data are distributed across groups. This is different from a Bar Chart. Like a bar chart, a histogram is made up of columns but with no gaps between the columns. Histograms present continuous data while bar chart presents categorical data (data that fits into categories).
When to use — To understand the distribution of data.
Histogram Chart Visual -
Some dos and don’t s of charts –
1. Remove useless visual clutter (Data-Ink Ratio Principle by Edward Tufte)
2. Avoid using 3D visual effects.
3. Let the data scream, speak I mean — Highlight where necessary.
4. Label the information wherever possible(Avoid Acronyms).
5. Keeping in mind — Audience Male Majority and their Colour Vision Deficiency, restrict using too many colours, Tufte advises to limit it to 6 Max.
