The dual Y-axis charts raise many eyebrows in the data visualization circles. They are often considered to confuse and lead to wrong data interpretation. However, when you have limited real estate and you want to quickly establish the relationship between 2 variables, the dual Y-axis chart can come in quite handy.
Using a dual Y-axis chart, you can easily validate/invalidate relations between two variables with different magnitudes and scales of measurement, as well as gauge a general idea of the trend.
However, use it with discretion. Here are four key tips for using the dual Y-axis chart:
1. Use the Y-axis on the left for the primary variable and the one on the right for the secondary variable
Our brains are conditioned to look for the Y-axis on the left of a chart. To take advantage of this, use the Y-axis on the left for the more important variable.
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