Bubble Plot

Use Bubble Plot to explore the relationship between two variables where the size of each symbol, or bubble, represents the size of a third variable.

For information about data considerations, examples, and interpretation, go to Overview for Bubble Plot.

Variables

You can graph the x and y-variables as individual pairs or you can graph every combination of the x-y variables. The y-variable is the variable that you want to explain or predict. The x-variable is a corresponding variable that might explain or predict changes in the y-variable. All columns must be numeric and must have the same number of rows.

First, choose one of the following options.

Each Y versus each X: Select to display a separate graph for each possible combination of x and y-variables that you enter.
XY Pairs: Select to display a separate graph for each pair of x and y-variables that you enter.

Then, enter the variables.

Y variables: Select the variables that you want to explain or predict.
X variables: Select the variables that might explain or predict the changes in the Y variables.

Bubble Size

Enter a column that determines the size (area) of the bubbles.

Layout

Choose a layout option.

Separate graphs for each XY pair: Creates a separate bubble plot for each XY pair.
Overlay XY pairs: Each XY pair is overlaid on a single bubble plot.

Group variable

Enter a variable that defines the groups. Group labels are shown in the graph legend.

By variables

Enter one or more grouping variables in By variables to create a separate bubble plot for each level of the grouping variables. The columns that you enter can be numeric or text, and must be the same length as the columns in Y variables and X variables. The y-scales for each variable are the same across the multiple bubble plots.

Show all combinations

When you enter multiple By variables, Minitab enables the Show all combinations checkbox. Select this option to create a separate bubble plot for each combination of groups created by the By variables. If you do not select this option, Minitab creates a plot for each group of each By variable.

For example, the first By variable has 2 groups, Male and Female, and the second By variable has 2 groups, Employed and Unemployed. If you select Show all combinations, Minitab creates 4 separate plots for the combinations of Male/Employed, Male/Unemployed, Female/Employed, and Female/Unemployed. If you do not select Show all combinations, Minitab creates 4 separate plots for Male, Female, Employed, and Unemployed.

Scale

Use the same scale across multiple graphs. These options are available only when you enter more than one pair of columns in X variables and Y variables and the layout is set to display separate graphs for each XY pair.

Same Y-scale: Use the same Y-scale across all graphs.
Same X-scale: Use the same X-scale across all graphs.

Log transformation

A logarithmic scale linearizes logarithmic relationships by changing the axis, so that the same distance represents different changes in value across the scale. For example, in the bubble plot with the untransformed x-scale, the function y = log(x) is not linear. When you transform the x-scale to logarithm base 10, the form of the data is linear. These options are only available for positive data.

Log transformation: Y-scale: Select to transform the Y-scale using logarithm base 10.
Log transformation: X-scale: Select to transform the X-scale using logarithm base 10.