graphics (version 3.3)

stripchart: 1-D Scatter Plots

Description

stripchart produces one dimensional scatter plots (or dot plots) of the given data. These plots are a good alternative to boxplots when sample sizes are small.

Usage

stripchart(x, ...)
## S3 method for class 'formula':
stripchart(x, data = NULL, dlab = NULL, \dots,
           subset, na.action = NULL)

## S3 method for class 'default':
stripchart(x, method = "overplot", jitter = 0.1, offset = 1/3,
           vertical = FALSE, group.names, add = FALSE,
           at = NULL, xlim = NULL, ylim = NULL,
           ylab = NULL, xlab = NULL, dlab = "", glab = "",
           log = "", pch = 0, col = par("fg"), cex = par("cex"),
           axes = TRUE, frame.plot = axes, ...)

Arguments

x

the data from which the plots are to be produced. In the default method the data can be specified as a single numeric vector, or as list of numeric vectors, each corresponding to a component plot. In the formula method, a symbolic specification of the form y ~ g can be given, indicating the observations in the vector y are to be grouped according to the levels of the factor g. NAs are allowed in the data.

data

a data.frame (or list) from which the variables in x should be taken.

subset

an optional vector specifying a subset of observations to be used for plotting.

na.action

a function which indicates what should happen when the data contain NAs. The default is to ignore missing values in either the response or the group.

...

additional parameters passed to the default method, or by it to plot.window, points, axis and title to control the appearance of the plot.

method

the method to be used to separate coincident points. The default method "overplot" causes such points to be overplotted, but it is also possible to specify "jitter" to jitter the points, or "stack" have coincident points stacked. The last method only makes sense for very granular data.

jitter

when method = "jitter" is used, jitter gives the amount of jittering applied.

offset

when stacking is used, points are stacked this many line-heights (symbol widths) apart.

vertical

when vertical is TRUE the plots are drawn vertically rather than the default horizontal.

group.names

group labels which will be printed alongside (or underneath) each plot.

add

logical, if true add the chart to the current plot.

at

numeric vector giving the locations where the charts should be drawn, particularly when add = TRUE; defaults to 1:n where n is the number of boxes.

ylab, xlab

labels: see title.

dlab, glab

alternate way to specify axis labels: see Details.

xlim, ylim

plot limits: see plot.window.

log

on which axes to use a log scale: see plot.default

pch, col, cex

Graphical parameters: see par.

axes, frame.plot

Axis control: see plot.default.

Details

Extensive examples of the use of this kind of plot can be found in Box, Hunter and Hunter or Seber and Wild.

The dlab and glab labels may be used instead of xlab and ylab if those are not specified. dlab applies to the continuous data axis (the X axis unless vertical is TRUE), glab to the group axis.

Examples

x <- stats::rnorm(50)
xr <- round(x, 1)
stripchart(x) ; m <- mean(par("usr")[1:2])
text(m, 1.04, "stripchart(x, "overplot")")
stripchart(xr, method = "stack", add = TRUE, at = 1.2)
text(m, 1.35, "stripchart(round(x,1), "stack")")
stripchart(xr, method = "jitter", add = TRUE, at = 0.7)
text(m, 0.85, "stripchart(round(x,1), "jitter")")

stripchart(decrease ~ treatment,
    main = "stripchart(OrchardSprays)",
    vertical = TRUE, log = "y", data = OrchardSprays)

stripchart(decrease ~ treatment, at = c(1:8)^2,
    main = "stripchart(OrchardSprays)",
    vertical = TRUE, log = "y", data = OrchardSprays)