lessR (version 2.3.1)

BoxPlot: Boxplot

Description

Abbreviation: bx

Uses the standard R boxplot function, boxplot to display a boxplot in color. Also display the relevant statistics such as the hinges, median and IQR.

If the provided object for which to calculate the box plot is a data frame, then a box plot is calculated for each numeric variable in the data frame and the results written to a pdf file in the current working directory. The name of this file and its path are specified in the output.

Usage

BoxPlot(x=NULL, dframe=mydata, ...)
## S3 method for class 'data.frame':
bx(x, \ldots) 
## S3 method for class 'default':
bx(x, col.box=NULL, col.pts=NULL, 
        col.bg=NULL, col.grid=NULL,
        colors=c("blue", "gray", "rose", "green", "gold", "red"), 
        cex.axis=.85, col.axis="gray30", col.ticks="gray30",
        horiz=TRUE, dotplot=FALSE,
        xlab=NULL, main=NULL, digits.d=NULL, ...)
bx(...)
color.boxplot(...)

Arguments

x

Variable for which to construct the histogram. Can be a data frame. If not specified with dframe, that is, no variable specified, then the data frame mydata is assumed.

dframe

Optional data frame that contains the variables of interest, default is mydata.

col.box

Color of the box.

col.pts

Color of any points that designate outliers. By default this is the same color as the box.

col.bg

Color of the plot background.

col.grid

Color of the grid lines.

colors

Sets the color palette.

cex.axis

Scale magnification factor, which by defaults displays the axis values to be smaller than the axis labels. Provides the functionality of, and can be replaced by, the standard R cex.axis.

col.axis

Color of the font used to label the axis values.

col.ticks

Color of the ticks used to label the axis values.

horiz

Orientation of the boxplot. Set FALSE for vertical.

dotplot

If TRUE, then place a dot plot (i.e., stripchart) over the box plot.

xlab

Label for the value axis, which defaults to the variable's name.

main

Title of graph.

digits.d

Number of decimal digits displayed in the listing of the summary statistics.

...

Other parameter values for graphics as defined processed by boxplot and par, including ylim to set the limits of the value axis,

Details

Unlike the standard R boxplot function, boxplot, the default here is for a horizontal boxplot. Also, BoxPlot does not currently process in formula mode, so use the standard R boxplot function to process a formula in which a boxplot is displayed for a variable at each level of a second, usually categorical, variable.

To obtain a box plot of each numerical variable in the mydata data frame, use BoxPlot(). Or, for a data frame with a different name, insert the name between the parentheses.

If the variable is in a data frame, the input data frame has the assumed name of mydata. If this data frame is named something different, then specify the name with the dframe option. Regardless of its name, the data frame need not be attached to reference the variable directly by its name, that is, no need to invoke the mydata$name notation. If no variable is specified, then all numeric variables in the entire data frame are analyzed and the results written to a pdf file.

Other graphic parameters are available to format the display, such as main for the title, and other parameters found in boxplot and par.

A labels data frame named mylabels, obtained from the lessR Read function, can list the label for some or all of the variables in the data frame that contains the data for the analysis. If this labels data frame exists, then the corresponding variable label is listed as the title of the resulting plot, unless a specific label is listed with the main option. The variable label is also listed in the text output, next to the variable name.

To minimize white space around the boxplot, re-size the graphics window before or after creating the boxplot.

The default background color of col.bg=ghostwhite provides a very mild cool tone with a slight emphasis on blue. The entire color theme can be specified at the system level with the lessR function set using the colors option. Or, use the same option for BoxPlot to set the color theme just for one box plot. The default color theme is blue, but a gray scale is available with "gray", and other themes are available as explained in the help function for set.

See Also

boxplot, par, set.

Examples

# simulate data and get at least one outlier
y <- rnorm(100,50,10)
y[1] <- 90


# -----------------------------
# boxplot for a single variable
# -----------------------------

# standard horizontal boxplot with all defaults
BoxPlot(y)

# short name
bx(y)

# vertical boxplot with plum color
BoxPlot(y, horiz=FALSE, col.box="plum")

# boxplot with outliers more strongly highlighted
BoxPlot(y, col.pts="red", xlab="My Variable")


# -----------------------------------------------
# boxplots for data frames and multiple variables
# -----------------------------------------------

# create data frame, mydata, to mimic reading data with rad function
# mydata contains both numeric and non-numeric data
mydata <- data.frame(rnorm(100), rnorm(100), rnorm(100), rep(c("A","B"),50))
names(mydata) <- c("X","Y","Z","C")

# boxplot for variable X from data frame, referred to directly
BoxPlot(X)

# boxplot with superimposed dot plot (stripchart)
BoxPlot(X, dotplot=TRUE)

# boxplots for all numeric variables in data frame called mydata
BoxPlot()

# boxplots for all numeric variables in data frame called mydata
#  with specified options
BoxPlot(col.box="palegreen1", col.pts="plum")

# Use the subset function to specify a variable list
mysub <- subset(mydata, select=c(X,Y))
BoxPlot(dframe=mysub)