R: Box Plots from Summaries

bxp {base} | R Documentation

## Box Plots from Summaries

### Description

`bxp` draws box plots based on the given summaries in `z`. It is usually called from within `boxplot`, but can be invoked directly.

### Usage

    bxp(z, notch = FALSE, width = NULL, varwidth = FALSE, outline = TRUE,
        notch.frac = 0.5, boxwex = 0.8, border = par("fg"), col = NULL,
        log = "", pars = NULL, frame.plot = axes, horizontal = FALSE, add = FALSE,
        at = NULL, show.names=NULL, ...)

### Arguments

`z` | a list containing data summaries to be used in constructing the plots. These are usually the result of a call to `boxplot`, but can be generated in any fashion.
`notch` | if `notch` is `TRUE`, a notch is drawn in each side of the boxes. If the notches of two plots do not overlap then the medians are significantly different at the 5 percent level.
`width` | a vector giving the relative widths of the boxes making up the plot.
`varwidth` | if `varwidth` is `TRUE`, the boxes are drawn with widths proportional to the square-roots of the number of observations in the groups.
`outline` | if `outline` is not true, the boxplot lines are not drawn.
`boxwex` | a scale factor to be applied to all boxes. When there are only a few groups, the appearance of the plot can be improved by making the boxes narrower.
`notch.frac` | numeric in (0,1). When `notch=TRUE`, the fraction of the box width that the notches should use.
`border` | character, the color of the box borders. Is recycled for multiple boxes.
`col` | character; the color within the box. Is recycled for multiple boxes
`log` | character, indicating if any axis should be drawn in logarithmic scale, as in `plot.default`.
`frame.plot` | logical, indicating if a ``frame'' (`box`) should be drawn; defaults to `TRUE`, unless `axes = FALSE` is specified.
`horizontal` | logical indicating if the boxplots should be horizontal; default `FALSE` means vertical boxes.
`add` | logical, if true add boxplot to current plot.
`at` | numeric vector giving the locations where the boxplots should be drawn, particularly when `add = TRUE`; defaults to `1:n` where `n` is the number of boxes.
`show.names` | Set to `TRUE` or `FALSE` to override the defaults on whether an x-axis label is printed for each group.
`pars,...` | Graphical parameters can be passed as arguments to this function, either as a list (`pars`) or normally(`...`).

### Value

An invisible vector, actually identical to the `at` argument, with the coordinates ("x" if horizontal is false, "y" otherwise) of box centers, useful for adding to the plot.

### Examples

    set.seed(753)
    str(bx.p <- boxplot(split(rt(100, 4), gl(5,20))))
    op <- par(mfrow= c(2,2))
    bxp(bx.p, xaxt = "n")
    bxp(bx.p, notch = TRUE, axes = FALSE, pch = 4)
    bxp(bx.p, notch = TRUE, col= "lightblue", frame= FALSE, outl= FALSE,
        main = "bxp(*, frame= FALSE, outl= FALSE)")
    bxp(bx.p, notch = TRUE, col= "lightblue", border="red", ylim = c(-4,4),
        pch = 22, bg = "green", log = "x", main = "... log='x', ylim=*")
    par(op)
    op <- par(mfrow= c(1,2))
    data(PlantGrowth)
    ## single group -- no label
    boxplot(weight~group,data=PlantGrowth,subset=group=="ctrl")
    bx<-boxplot(weight~group,data=PlantGrowth,subset=group=="ctrl",plot=FALSE)
    ## with label
    bxp(bx,show.names=TRUE)
    par(op)

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