The box plot can be used for comparing a limited number of quantiles to summarize each distribution. Box plots can be made to display the variability of the median and can have variable widths to represent differences in sample sizes. This plot uses the function bwplot for the underlying computations.
To generate a box plot
Choose Graph Two Variable
Box Plot. The dialog shown below appears.
Data page
In the Box Plot dialog, the Data page has the following options:
Data
Data Set
Select a data set from the dropdown list or type the name of a data set. You can also type into the Data Set edit field any expression that evaluates to a data set.
Enter an S-PLUS expression that identifies the rows to use in the analysis. To use all the rows in the data set, leave this field blank.
Variables
Value
Specify the column of numeric values used to construct the boxplot.
Category
Specify a grouping column used to separate the values into multiple boxes.
Conditioning
Select the columns specifying conditioning values.
Save Graph Object
Enter the name for the object in which to save the results of the analysis.
Plot page
In the Box Plot dialog, the Plot page has the following options:
Box Width
Box Ratio
Specify the ratio of box width to inter-box space.
Symbol
Symbol Color Choose the color for the center dot.
Symbol Style Choose the symbol style for the center dot.
Symbol Size Choose the symbol size for the center dot.
Titles page
In the Box Plot dialog, the Titles page has the following options:
Titles
Main Title
Specify a main title to add on the top of the page.
Subtitle
Specify a subtitle to add on the bottom of the page.
Labels
X Axis Label
Specify a label for the x-axis.
Y Axis Label
Specify a label for the y-axis.
Axes page
In the Box Plot dialog, the Axes page has the following options:
Aspect Ratio
Aspect Ratio This controls the size of the axis area within the designated plot area. Specify "Fill Plot Area" to fill the page, "Bank to 45 Degrees" to use the 45-degree banking rule in each panel, or "Specified Value" to specify a numeric value.
Ratio Value A numeric value indicating the ratio of height to width.
Scale
X Scale
The scale to use for placing tick marks on the x-axis.
Y Scale
The scale to use for placing tick marks on the y-axis.
Limits
X Limits
The limits for the x-axis. Specify a minimum and a maximum, separated by a comma. For example: "1, 10".
Y Limits
The limits for the y-axis. Specify a minimum and a maximum, separated by a comma. For example: "1, 10".
Relation
X Relation
Controls the relationship between the x-axes in different panels of a conditioned plot. The default value of "Same" ensures that the horizontal or vertical axes on each panel will be identical. "Sliced" gives the same number of data units to corresponding axes on each panel, ensuring that the number of units per cm. is identical. "Free" results in each panel having an axis that accommodates just the data in that panel. For "Sliced" and "Free", axes will be drawn for each panel, using more space on the display.
Y Relation
Controls the relationship between the y-axes in different panels of a conditioned plot.
Alternating
Alternating X Axes
Determines whether x-axes alternate from one side of the group of panels to the other.
Alternating Y Axes
Determines whether y-axes alternate from one side of the group of panels to the other.
Multipanel page
In the Box Plot dialog, the Multipanel page has the following options:
Layout
Number of Columns/Rows/Pages Control the layout of the panels by specifying the number of columns, rows and pages. Choose Auto for automatic calculation.
Panel Order Choose from Graph Order or Table Order. Graph Order begins drawing panels in the bottom left corner of the graph, to the right and up. Table Order begins drawing panels in the upper left corner and continues right.
Include Strip Labels Check this to include strip labels on panels.
Continuous Conditioning
Number of Panels If the data are continuous, the number of panels is determined by the number specified in this field.
Overlap Fraction Create overlapping intervals by specifying the fraction of data points that are shared across two panels.
Interval Type Choose from Equal Counts or Equal Ranges. Equal Counts places an equal number of data points in each plot. Equal Ranges makes the interval widths all equal.