# interactionPlots: Interactions Plot for Two-way Analysis of Variance In s20x: Functions for University of Auckland Course STATS 201/208 Data Analysis

## Description

Displays data with intervals for each combination of the two factors and shows the mean differences between levels of the first factor for each level of the second factor. Note that there should be more than one observation for each combination of factors.

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46``` ```interactionPlots(y, ...) ## Default S3 method: interactionPlots( y, fac1 = NULL, fac2 = NULL, xlab = NULL, xlab2 = NULL, ylab = NULL, data.order = TRUE, exlim = 0.1, jitter = 0.02, conf.level = 0.95, interval.type = c("tukey", "hsd", "lsd", "ci"), pooled = TRUE, tick.length = 0.1, interval.distance = 0.2, col.width = 2/3, xlab.distance = 0.1, xlen = 1.5, ylen = 1, ... ) ## S3 method for class 'formula' interactionPlots( y, data = NULL, xlab = NULL, xlab2 = NULL, ylab = NULL, data.order = TRUE, exlim = 0.1, jitter = 0.02, conf.level = 0.95, interval.type = c("tukey", "hsd", "lsd", "ci"), pooled = TRUE, tick.length = 0.1, interval.distance = 0.2, col.width = 2/3, xlab.distance = 0.1, xlen = 1.5, ylen = 1, ... ) ```

## Arguments

 `y` either a formula of the form: y~fac1+fac2 where y is the response and fac1 and fac2 are the two explanatory variables used as factors, or a single response vector `...` optional arguments. `fac1` if 'y' is a vector, then fac1 contains the levels of factor 1 which correspond to the y value `fac2` if 'y' is a vector, then fac1 contains the levels of factor 2 which correspond to the y value `xlab` an optional label for the x-axis. If not specified the name of fac1 will be used. `xlab2` an optional label for the lines. If not specified the name of fac2 will be used. `ylab` An optional label for the y-axis. If not specified the name of y will be used. `data.order` if TRUE the levels of fac1 and fac2 will be set to unique(fac1) and unique(fac2) respectively. `exlim` provide extra limits. `jitter` the amount of horizontal jitter to show in the plot. The actual jitter is determined as the function is called, and will likely be different each time the function is used. `conf.level` confidence level of the intervals. `interval.type` four options for intervals appearing on plot: 'tukey', 'hsd', 'lsd' or 'ci'. `pooled` two options: pooled or unpooled standard deviation used for plotted intervals. `tick.length` size of tick, in inches. `interval.distance` distance, as a fraction of the column width, between the points and interval. This is in addition to the extra space allocated for the jitter. `col.width` width of a factor ‘column’, as a fraction of the space between the centres of two columns. `xlab.distance` distance of x-axis labels from bottom of plot, as a fraction of the overall height of the plot. `xlen, ylen` character interspacing factor for horizontal (x) and vertical (y) spacing of the legend. `data` an optional data frame containing the variables in the model.

## Methods (by class)

• `default`: Interactions Plot for Two-way Analysis of Variance

• `formula`: Interactions Plot for Two-way Analysis of Variance

`summary2way`.
 ```1 2 3 4 5 6``` ```data(mtcars) interactionPlots(wt ~ vs + gear, mtcars) ## note this usage is deprecated data(mtcars) with(mtcars, interactionPlots(wt, vs, gear)) ```