itemFrequencyPlot {arules} | R Documentation

## 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 signature 'itemMatrix':
    itemFrequencyPlot(x, type = c("relative", "absolute"),
        support = NULL, topN = NULL,
        population = NULL, popCol = "black", popLwd = 1,
        lift = FALSE, horiz = FALSE,
        names = TRUE, cex.names =  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.
`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

    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)

[Package arules version 0.6-3 Index]