When to use linear or logarithmic axis in charts
Have you tried changing ‘Axis type’ between ‘Linear’ or ‘Lograthimic’ while you create a chart in Excel, Google Sheets, Tableau, or Python libraries like Matplotlib?
In this blog let me briefly explain when to use Linear / Lograthamic. In both types, the creator will plot the same columns on the x-axis & y-axis. Here I have plotted a line chart with data about covid-19 deaths between Feb 15 till Apr 18.
- y-axis — no of deaths (which you want to aggregate)
- x-axis — date (represent time)
Linear Axis
When to use
- When the data has a relatively small range E.g. A 50-day date range means 50 axis points in the x-axis. (or)
- When the rate of change is constant i.e. fairly judgable increase or decrease. E.g. Gold price constantly increases over 100 years; the same for global temperature increases over 300 years. (or)
- When the focus is on comparing absolute values. E.g. Compare revenue generated by 3 different companies in the last 5 years.
Visualization
- The values in the y-axis on the chart are equally spaced at regular intervals. As you see in the image — 0, 10K, 20K, 30K, 40K, …
Linear axis makes it easy to understand and interpret the data, as the difference between any two consecutive values is constant.
Logarithmic Axis
When to use
- When the data has a large range. A larger date range means more than 50 axis points to any number (or)
- When the rate of change is exponential. A sudden unexpected spike in the y-axis and unexpected downfall. E.g. Covid-19 cases surge to a higher number and came down or stock prices always have unexpected spikes and downfall frequently.
- When the focus is on comparing relative growth rates or percentage changes. Comparing the relative growth rates (percentage changes) of 2 or more items, which can vary significantly. E.g. Different social media apps gain popularity and at a time lose popularity. An advertising agency would analyze the Year-on-Year growth of social media platforms to plan ad submissions with the best ROI making social media.
Visualization
- The values on the chart are spaced based on their logarithmic values (usually using base 10).
Lograthimic axis compresses the higher values and expands the lower values, making it easier to identify trends and patterns in data with wide-ranging values.
Share in comments which concepts you wish to see in a simple explanation with examples.
