arules (version 1.6-8)

itemFrequencyPlot: Creating a Item Frequencies/Support Bar Plot

Description

Provides the generic function itemFrequencyPlot and the S4 method to create an item frequency bar plot for inspecting the item frequency distribution for objects based on '>itemMatrix (e.g., '>transactions, or items in '>itemsets and '>rules).

Usage

itemFrequencyPlot(x, …)
# S4 method for itemMatrix
itemFrequencyPlot(x, type = c("relative", "absolute"), 
    weighted = FALSE, support = NULL, topN = NULL,
    population = NULL, popCol = "black", popLwd = 1,
    lift = FALSE, horiz = FALSE, 
    names = TRUE, cex.names =  graphics::par("cex.axis"), 
    xlab = NULL, ylab = NULL, mai = NULL, …)

Arguments

x

the object to be plotted.

…

further arguments are passed on (see barplot from possible arguments).

type

a character string indicating whether item frequencies should be displayed relative of absolute.

weighted

should support be weighted by transactions weights stored as column "weight" in transactionInfo?

support

a numeric value. Only display items which have a support of at least support. If no population is given, support is calculated from x otherwise from the population. Support is interpreted relative or absolute according to the setting of type.

topN

a integer value. Only plot the topN items with the highest item frequency or lift (if lift = TRUE). The items are plotted ordered by descending support.

population

object of same class as x; if x is a segment of a population, the population mean frequency for each item can be shown as a line in the plot.

popCol

plotting color for population.

popLwd

line width for population.

lift

a logical indicating whether to plot the lift ratio between instead of frequencies. The lift ratio is gives how many times an item is more frequent in x than in population.

horiz

a logical. If horiz = FALSE (default), the bars are drawn vertically. If TRUE, the bars are drawn horizontally.

names

a logical indicating if the names (bar labels) should be displayed?

cex.names

a numeric value for the expansion factor for axis names (bar labels).

xlab

a character string with the label for the x axis (use an empty string to force no label).

ylab

a character string with the label for the y axis (see xlab).

mai

a numerical vector giving the plots margin sizes in inches (see `? par').

Value

A numeric vector with the midpoints of the drawn bars; useful for adding to the graph.

See Also

itemFrequency, itemMatrix-class

Examples

# NOT RUN {
data(Adult)

## the following example compares the item frequencies
## of people with a large income (boxes) with the average in the data set
Adult.largeIncome <- Adult[Adult %in% 
	"income=large"]

## simple plot
itemFrequencyPlot(Adult.largeIncome)

## plot with the averages of the population plotted as a line 
## (for first 72 variables/items)
itemFrequencyPlot(Adult.largeIncome[, 1:72], 
	population = Adult[, 1:72])

## plot lift ratio (frequency in x / frequency in population)
## for items with a support of 20% in the population
itemFrequencyPlot(Adult.largeIncome, 
        population = Adult, support = 0.2, 
	lift = TRUE, horiz = TRUE)
# }