plot.freqtab function

Plotting Frequency Distributions

This function plots univariate and bivariate frequency tables of class ‘freqtab’ .

## S3 method for class 'freqtab'
plot(
  x,
  y = NULL,
  xcol = 1,
  ycol,
  pch = 16,
  ylty = 1,
  xlab = names(dimnames(x))[1],
  addlegend = !missing(y),
  legendtext,
  ...
)

## S3 method for class 'freqtab'
points(x, xcol = 1, pch = 16, ds = 50, dm = 100, ...)

Arguments

• x: univariate or bivariate score distribution of class ‘freqtab’ .

• y: either an object of class ‘freqtab’ , where frequencies will be extracted, or a vector or matrix of frequencies, to be added to the plot of x. See below for details.

• xcol, ycol: colors used in plotting x and y.

• pch: plotting symbol used to plot bivariate points.

• ylty: line type used to plot frequencies in y.

• xlab: label for the x axis.

• addlegend: logical indicating whether or not a legend should be added.

• legendtext: character vector of text to be passed to the legend

  argument of the legend function, defaulting to column names used in y.

• ...: further arguments passed to or from other methods, such as graphical parameters besides col, type, and pch.

• ds, dm: integers for the scaling and center of the RGB density values, with defaults of 50 and 100. These are used to convert the observed counts in x to the [0, 255] range of RGB values.

Returns

The univariate option produces a single line plot of type = "h". Frequencies from y are then superimposed. The bivariate option produces a scatterplot with a marginal frequency plot for each distribution.

Details

For the points method, a scatterplot for x is added to the current opened plot.

For the plot method, when x is univariate, i.e, having 2 columns, a frequency plot is created for x. When x is bivariate, e.g., coming from a single group equating design or one form of a nonequivalent groups design, a scatterplot is produced with frequency plots for the marginal distributions.

y is used to superimpose lines, e.g., smoothed frequencies, over the (marginal) frequencies of x.

Colors must be specified using xcol and ycol. When ycol

is missing, a vector of colors is created using rainbow(ncol(y)).

Examples

x <- freqtab(KBneat$x, scales = list(0:36, 0:12))
plot(x)

xs <- loglinear(x, degrees = c(4, 1),
  stepup = TRUE, showWarnings = FALSE)
plot(x, xs, lwd = 2)

See Also

plot.table, plot.equate, lines, points

Author(s)

Anthony Albano tony.d.albano@gmail.com