Scatterplot

From Business Intelligence

Simple scatterplot with no gridlines, light gray axes, and a muted color for the dots.	This Tufte-style dot-dash scatterplot places dashes on the axes to mark the data points. This makes good use of the axes and increases data density by affording another way of looking at the distribution. Excel charts designed by William Oswald. Retrieved on 06/03/08.	This interactive scatterplot has a wealth of information about 2005 Mass private schools. It integrates bubbles and has many different variables that the user can manipulate to investigate the data. Alternatively, in a static image this dataset could be a good candidate for a multiset scatterplot with each set having a different color.
This bubble chart showing OU Web Referrers Oct 2007 gives a good idea of the composition of the web referrers. Its interactivity also makes it possible to get detail from each element, whereas a static bubble chart would suffer from an inability to identify all the bubbles.	This is a Tufte-compatible bubble chart. Its source data values vary widely, which makes it a good candidate for a bubble chart. It features clean formatting and is not 3D, which is important as distortion is especially likely for spherical shapes.

Description

Also known as a scatter graph or dot chart. Scatterplots show relationships and correlations between two quantitative variables. Common scatterplots are mapped on a Cartesian coordinate system as dots scattered across the plane. Use this to visualize relationships between variables. It can represent large datasets with exceptions, such as outliers. It is especially useful for seeing trends in the data.

Considerations

For scatterplots

It is especially important to eliminate or minimize grid lines in scatter plots, as the data points are dots that can be hard to see.
To increase clarity of the graphic, try a dot-dash plot, which puts dashes on the axes corresponding to where the points are.
Try showing just the range of the plotted data on the axes rather than the whole range.

For bubble plots

Does not work well with a range that includes negative numbers
Does not convey exact values
People have a hard time visually distinguishing size differences between circles

Related techniques

Bubble chart: This variant uses area size to encode a value. Commonly, it is shown on an x-y axis. However, another way to employ the bubble chart is as a chart that displays values as circles of varying size but arranged arbitrarily. Good for comparing a set of values, especially when the values differ greatly. It can also be interactive - if there is more than one dimension the user can pick which dimension to display, such as at Gapminder.

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