The SGPANEL Procedure

DENSITY Statement

Creates a density curve that shows the distribution of values in your data.

Interaction:	The DENSITY statement can be combined only with the DENSITY and HISTOGRAM statements in the SGPANEL procedure.
Featured in:	Creating a Panel of Graph Cells with Histograms and Density Plots

Syntax

DENSITY response-variable < / option(s)>;

option(s) can be one or more options from the following categories:

DENSITY options:

FREQ= numeric-variable

LINEATTRS= style-element < (options) > | (options)

SCALE= scaling-type

TYPE= NORMAL(option(s)) | KERNEL(option(s))
Plot options:

LEGENDLABEL= "text-string"

NAME= "text-string"

TRANSPARENCY= numeric-value

Required Arguments

response-variable: specifies the variable for the x axis. The variable must be numeric.

Options

FREQ= numeric-variable

specifies that each observation is repeated n times for computational purposes, where n is the value of the numeric variable. If n is not an integer, then it is truncated to an integer. If n is less than 1 or missing, then it is excluded from the analysis.

LEGENDLABEL= "text-string"

specifies a label that identifies the density plot in the legend. By default, the label identifies the type of density curve. If you specify TYPE=NORMAL, then the default label is "Normal." If you specify TYPE=KERNEL, then the default label is "Kernel."

Note: User-specified parameters from the TYPE= option are included in the label by default. [cautionend]

LINEATTRS= style-element <(options)> | (options)

specifies the appearance of the density line. You can specify the appearance by using a style element or by using suboptions. If you specify a style element, you can additionally specify suboptions to override specific appearance attributes.

options can be one or more of the following:

COLOR= color

specifies the color of the line. For more information about specifying colors, see SAS/GRAPH Colors and Images in the SAS/GRAPH: Reference, Second Edition.

Default:

The default color is specified by the ContrastColor attribute of the GraphFit style element in the current style.

PATTERN= line-pattern

specifies the line pattern for the line. You can reference SAS patterns by number or by name. See Line Patterns for a list of line patterns.

Default:

The default line pattern is specified by the LineStyle attribute of the GraphFit style element in the current style.

THICKNESS= n <units>

specifies the thickness of the line. You can also specify the unit of measure. The default unit is pixels. See Units of Measurement for a list of the measurement units that are supported.

Default:

The default line thickness is specified by the LineThickness attribute of the GraphFit style element in the current style.

NAME= "text-string"

specifies a name for the plot. You can use the name to refer to this plot in other statements.

SCALE= COUNT | DENSITY | PERCENT | PROPORTION

specifies the scaling that is used for the response axis. Specify one of the following values:

COUNT: the axis displays the frequency count.
DENSITY: the axis displays the density estimate values.
PERCENT: the axis displays values as a percentage of the total.
PROPORTION: the axis displays values in proportion to the total.

Default:

PERCENT

TRANSPARENCY= numeric-value

specifies the degree of transparency for the density curve. Specify a value from 0.0 (completely opaque) to 1.0 (completely transparent).

Default:

0.0

TYPE = NORMAL < (normal-opts)>| KERNEL < (kernel-opts)>

specifies the type of distribution curve that is used for the density plot. Specify one of the following keywords:

NORMAL < (normal-opts)>

specifies a normal density estimate, with a mean and a standard deviation.

normal-opts can be one or more of the following values:

MU= numeric-value: specifies the mean value that is used in the density function equation. By default, the mean value is calculated from the data.
SIGMA= numeric-value: specifies the standard deviation value that is used in the density function equation. The value that you specify for the SIGMA= suboption must be a positive number. By default, the standard deviation value is calculated from the data.

KERNEL < (kernel-opts)>

specifies a nonparametric kernel density estimate.

kernel-opts can be:

C= numeric-value

specifies the standardized bandwidth for a number that is greater than 0 and less than or equal to 100.

The value that you specify for the C= suboption affects the value of [lambda] as shown in the following equation:

[equation]

In this equation c is the standardized bandwidth, Q is the interquartile range, and n is the sample size.

WEIGHT= NORMAL | QUADRATIC | TRIANGULAR

specifies the weight function. You can specify either normal, quadratic, or triangular weight function.

Default:

NORMAL

Default:

NORMAL

Details

Normal Density Function

When the type of the density curve is NORMAL, the fitted density function equation is as follows:

[equation]

In the equation, [mu] is the mean, and [sigma] is the standard deviation. You can specify [mu] by using the MU= suboption and [sigma] by using the SIGMA= suboption.

Kernel Density Function

When the TYPE of the density curve is KERNEL, the general form of the kernel density estimator is as follows:

[equation]

In the equation, [equation] is the weight function, [lambda] is the bandwidth, n is the sample size, and is the ith observation. You can use the C= suboption to specify the bandwidth and the WEIGHT= suboption to specify the weight function .

Kernel Density Weight Functions

The formulas for the weight functions are as follows:

NORMAL

[equation]

QUADRATIC

[equation]

TRIANGULAR

[equation]

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	FREQ= numeric-variable
	LINEATTRS= style-element < (options) > \| (options)
	SCALE= scaling-type
	TYPE= NORMAL(option(s)) \| KERNEL(option(s))

	LEGENDLABEL= "text-string"
	NAME= "text-string"
	TRANSPARENCY= numeric-value