Interaction Plot

An interaction plot displays the levels of one factor along the x-axis, the response on the y-axis, and the points corresponding to a particular level of a second factor connected by lines. This type of plot is useful for exploring or discovering interactions.

Choose Statistics __image\arrow5.gif Design __image\arrow5.gif Interaction Plot from the main menu. The dialog shown below appears.

__image\interact.gif

The Interaction Plot has the following options:

Data Set

Select a data set from the dropdown list or type the name of a data set. You can also type into the Data Set edit field any expression that evaluates to a data set.

Subset Rows

Enter an S-PLUS expression that identifies the rows to use in the analysis. To use all the rows in the data set, leave this field blank.

Omit Rows with Missing Values

Select this box to omit from the analysis any rows in the data set that contain missing values for any of the variables in the model.

Variables

Choose a dependent and one or more independent variables. The dependent variable should be a continuous variable, and the independent variables should be factor variables.

Options

Both Orderings for Each Pair Choose whether to include both orderings of each pair of independent variables. That is, whether to plot all n*(n-1)/2 unique combinations.

Function Enter the univariate function of the dependent variable to use in the plot. Typical choices include mean, median, and variance. The default is mean.

Layout

Rows Select the number of rows per page in the graph layout.

Columns Select the number of columns per page in the graph layout.

Related programming language functions

MenuInteractionPlot, plot.design