Default Panel Function for xyplot

This is the default panel function for xyplot. Also see panel.superpose. The default panel functions for splom and qq are essentially the same function.

panel.xyplot(x, y, type = "p",
             groups = NULL,
             pch, col, col.line, col.symbol,
             font, fontfamily, fontface,
             lty, cex, fill, lwd,
             horizontal = FALSE, ...,
             smooth = NULL,
             grid = lattice.getOption("default.args")$grid,
             abline = NULL,
             jitter.x = FALSE, jitter.y = FALSE,
             factor = 0.5, amount = NULL,
             identifier = "xyplot")
panel.splom(..., identifier = "splom")
panel.qq(..., identifier = "qq")

Arguments

x,y

variables to be plotted in the scatterplot

type

character vector controlling how x and y are to be plotted. Can consist of one or more of the following: "p", "l", "h", "b", "o", "s", "S", "g", "r", "a", "smooth", and "spline". If type has more than one element, an attempt is made to combine the effect of each of the components.

The behaviour if any of the first five are included in type is similar to the effect of the corresponding type in plot: "p" and "l" stand for points and lines respectively; "b" and "o" (for ‘overlay’) plot both; "h" draws vertical (or horizontal if horizontal = TRUE) line segments from the points to the origin. Types "s" and "S" are like "l" in the sense that they join consecutive points, but instead of being joined by a straight line, points are connected by a vertical and a horizontal segment forming a ‘step’, with the vertical segment coming first for "s", and the horizontal segment coming first for "S". Types "s" and "S" sort the values along one of the axes (depending on horizontal); this is unlike the behavior in plot. For the latter behavior, use type = "s" with panel = panel.points.

Type "g" adds a reference grid using panel.grid in the background, but using the grid argument is now the preferred way to do so.

The remaining values of type lead to various types of smoothing. This can also be achieved using the smooth argument, or by calling the relevant panel functions directly. The panel functions provide finer control over graphical and other parameters, but using smooth or type is convenient for simple usage. Using smooth is recommended, but type is also supported for backwards compatibility.

Type "r" adds a linear regression line, "smooth" adds a loess fit, "spline" adds a cubic smoothing spline fit, and "a" draws line segments joining the average y value for each distinct x value. See smooth for details.

See example(xyplot) and demo(lattice) for examples.

groups

an optional grouping variable. If present, panel.superpose will be used instead to display each subgroup

col, col.line, col.symbol

default colours are obtained from plot.symbol and plot.line using trellis.par.get.

font, fontface, fontfamily

font used when pch is a character

pch, lty, cex, lwd, fill

other graphical parameters. fill serves the purpose of bg in points for certain values of pch

horizontal

A logical flag controlling the orientation for certain type's, e.g., "h", "s", ans "S" and the result of smoothing.

...

Extra arguments, if any, for panel.xyplot. Usually passed on as graphical parameters to low level plotting functions, or to the panel functions performing smoothing, if applicable.

smooth

If specificied, indicates the type of smooth to be added. Can be a character vector containing one or more values from "lm", "loess", "spline", and "average". Can also be a logical flag; TRUE is interpreted as "loess". Each of these result in calling a corresponding panel function as described below; the smooth argument simply provides a convenient shortcut.

"lm" adds a linear regression line (same as panel.lmline, except for default graphical parameters). "loess" adds a loess fit (same as panel.loess). "spline" adds a cubic smoothing spline fit (same as panel.spline). "average" has the effect of calling panel.average, which in conjunction with a groups argument can be useful for creating interaction plots.

Normally, smoothing is performed with the y variable as the response and the x variable as the predictor. However, the roles of x and y are reversed if horizontal = TRUE.

grid

A logical flag, character string, or list specifying whether and how a background grid should be drawn. This provides the same functionality as type="g", but is the preferred alternative as the effect type="g" is conceptually different from that of other type values (which are all data-dependent). Using the grid argument also allows more flexibility.

Most generally, grid can be a list of arguments to be supplied to panel.grid, which is called with those arguments. Three shortcuts are available:

TRUE:

roughly equivalent to list(h = -1, v = -1)

"h":

roughly equivalent to list(h = -1, v = 0)

"v":

roughly equivalent to list(h = 0, v = -1)

No grid is drawn if grid = FALSE.

abline

A numeric vector or more generally a list containing arguments that are used to call panel.abline. If specified as a numeric vector, abline is used as the first unnamed argument to panel.abline. This allows arguments of the form abline = c(0, 1), which adds the diagonal line, or abline = coef(fm) to fit the regression line from a fitted mode. Use the list form for finer control; e.g., abline = list(h = 0, v = 0, col = "grey").

For more flexibility, use panel.abline directly.

jitter.x, jitter.y

logical, whether the data should be jittered before being plotted.

factor, amount

controls amount of jittering.

identifier

A character string that is prepended to the names of grobs that are created by this panel function.

Details

Creates scatterplot of x and y, with various modifications possible via the type argument. panel.qq draws a 45 degree line before calling panel.xyplot.

Note that most of the arguments controlling the display can be supplied directly to the high-level (e.g. xyplot) call.

Author

Deepayan Sarkar Deepayan.Sarkar@R-project.org

Examples


types.plain <- c("p", "l", "o", "r", "g", "s", "S", "h", "a", "smooth")
types.horiz <- c("s", "S", "h", "a", "smooth")
horiz <- rep(c(FALSE, TRUE), c(length(types.plain), length(types.horiz)))

types <- c(types.plain, types.horiz)

x <- sample(seq(-10, 10, length.out = 15), 30, TRUE)
y <- x + 0.25 * (x + 1)^2 + rnorm(length(x), sd = 5)

xyplot(y ~ x | gl(1, length(types)),
       xlab = "type", 
       ylab = list(c("horizontal=TRUE", "horizontal=FALSE"), y = c(1/6, 4/6)),
       as.table = TRUE, layout = c(5, 3),
       between = list(y = c(0, 1)),
       strip = function(...) {
           panel.fill(trellis.par.get("strip.background")$col[1])
           type <- types[panel.number()]
           grid::grid.text(label = sprintf('"%s"', type), 
                           x = 0.5, y = 0.5)
           grid::grid.rect()
       },
       scales = list(alternating = c(0, 2), tck = c(0, 0.7), draw = FALSE),
       par.settings = 
       list(layout.widths = list(strip.left = c(1, 0, 0, 0, 0))),
       panel = function(...) {
           type <- types[panel.number()]
           horizontal <- horiz[panel.number()]
           panel.xyplot(..., 
                        type = type,
                        horizontal = horizontal)
       })[rep(1, length(types))]