interactionPlots {s20x}

Interactions Plot for Two-way Analysis of Variance

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

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)

• interactionPlots(default): Interactions Plot for Two-way Analysis of Variance

• interactionPlots(formula): Interactions Plot for Two-way Analysis of Variance

See Also

summary2way.

Examples

data(mtcars)
interactionPlots(wt ~ vs + gear, mtcars)

## note this usage is deprecated
data(mtcars)
with(mtcars, interactionPlots(wt, vs, gear))