Example Program and Statement Details

Example Graph

The following graph was generated by the Example Program:

Example Program

proc template;
  define statgraph loessplot;
    begingraph;
      entrytitle "Loess Fit Plot";
      layout overlay;
        scatterplot x=weight y=mpg_highway /
          datatransparency=.7;
        loessplot x=weight y=mpg_highway / name="fitline"
          alpha=.05 legendlabel="Loess Fit";
        discretelegend "fitline";
      endlayout;
    endgraph;
  end;
run;

proc sgrender data=sashelp.cars template=loessplot;
run;

Statement Summary

The LOESSPLOT statement only supports statistical models of one independent and one dependent variable. For more information about the fitting methodology, see the LOESS procedure in the MISSING Bookref .

In addition to the loess curve, the LOESSPLOT statement can compute confidence levels for the fitted line. To display the confidence levels,

use the CLM= option to declare a name for the confidence level of the mean
use a MODELBAND statement to refer this name. This statement draws a confidence band from this information. See MODELBAND Statement for information about how to control the appearance of the confidence band.

Required Arguments

X=numeric-column | expression

specifies the column for the X values.

Y=numeric-column | expression

specifies the column for the Y values.

Loess Regression Options

ALPHA= positive-number

specifies the confidence level to compute.

Default: .05

Range: 0 < number < 1

Range: ALPHA=.05 represents a 95% confidence level.

CLM= "name"

produces confidence limits for a mean predicted value for each observation. The confidence level is set by the ALPHA= option.

Default: no default

Interaction: "name" is a unique name within the template that is case sensitive and cannot contain spaces. It must be assigned in order for the confidence limits to be computed. To display confidence limits, you must use this name as the required argument of a MODELBAND statement.

DEGREE=1 | 2

specifies the degree of the local polynomials to use for each local regression. The valid values are 1 for local linear fitting or 2 for local quadratic fitting.

Default: 1

INTERPOLATION=LINEAR | CUBIC

specifies the degree of the interpolating polynomials used for blending local polynomial fits at the kd tree vertices.

Default: LINEAR

CUBIC

cubic polynomials

LINEAR

linear polynomials

MAXPOINTS= positive-integer

specifies the maximum number of predicted points generated for the loess curve as well as confidence limits.

Default: 201

SMOOTH=AUTO | positive-number

specifies a regression parameter value.

Default: AUTO

REWEIGHT=NONE | positive-integer

specifies the number of iterative re-weighting steps to be done. Such iterations are appropriate when there are outliers in the data or when the error distribution is a symmetric long-tailed distribution.

Default: NONE

WEIGHT= numeric-column

specifies a variable in the input data set that contains values to be used as a priori weights for a loess fit. The values of the weight variable must be nonnegative. If an observation’s weight is zero, negative, or missing, the observation is deleted from the analysis.

Default: no default

Options

Statement Option	Description
CURVELABEL	Specifies the label of the loess curve.
CURVELABELATTRS	Specifies the color and font attributes of the curve label.
CURVELABELLOCATION	Specifies the location of the curve label relative to the plot area.
CURVELABELPOSITION	Specifies the position of the curve label relative to the curve line.
DATATRANSPARENCY	Specifies the degree of the transparency of the loess curve.
GROUP	Creates a distinct set of curves from just the observations that correspond to each unique group value of the specified column.
INDEX	Specifies indices for mapping line attributes (color and pattern) to one of the GraphData1 - GranphDataN style elements.
LEGENDLABEL	Specifies a label for use in a legend.
LINEATTRS	Specifies the properties of the loess curve.
NAME	Assigns a name to a plot statement for reference in other template statements.
PRIMARY	Specifies that the data columns for this plot be used for determining default axis features.
TIPFORMAT	Specifies display formats for information defined by roles.
TIPLABEL	Specifies display labels for information defined by roles.
XAXIS	Specifies whether data are mapped to the primary X (bottom) axis or the secondary X2 (top) axis.
YAXIS	Specifies whether data are mapped to the primary Y (left) axis or the secondary Y2 (right) axis.

CURVELABEL="string"

specifies a label for the loess curve.

Default: no default

Interaction: If the GROUP= option is specified, this option is ignored.

The font and color attributes for the label are specified by the CURVELABELATTRS= option.

CURVELABELATTRS=style-element | style-element (text-options) | (text-options)

specifies the color and font attributes of the curve labels. See General Syntax for Attribute Options for the syntax on using a style-element and Text Options for available text-options.

Default: The GraphValueText style element.

Interaction: For this option to take effect, the CURVELABEL= option must also be specified.

Interaction: If the GROUP= option is specified, this option is ignored.

CURVELABELLOCATION=INSIDE | OUTSIDE

specifies the location of the curve label relative to the plot area.

Default: INSIDE

INSIDE

inside the plot area

OUTSIDE

outside the plot area

Restriction: OUTSIDE cannot be used when the LOESSPLOT is used in multicell layouts such as LATTICE, DATAPANEL, or DATALATTICE, where axes might be external to the grid.

Interaction: For this option to take effect, the CURVELABEL= option must also be specified.

Interaction: This option is used in conjunction with the CURVELABELPOSITION= option to determine where the curve labels appear. For more information, see Location and Position of Curve Labels.

CURVELABELPOSITION=AUTO | MAX | MIN | START | END

specifies the position of the curve label relative to the curve line.

Default: AUTO when CUVELABELLOCATION=OUTSIDE, and END when CURVELABELLOCATION=INSIDE

AUTO

Only used when CURVELABELPOSITION=OUTSIDE. The curve label is positioned automatically near the curve boundary along unused axes whenever possible (typically Y2 and X2) to avoid collision with tick values.

MAX

Forces the curve label to appear near maximum curve values (typically, upper right).

MIN

Forces the curve label to appear near minimum curve values (typically, lower left).

START

Only used when CURVELABELLOCATION=INSIDE. Forces the curve label to appear near the beginning of the curve. Particularly useful when the curve line has a spiral shape.

END

Only used when CURVELABELLOCATION=INSIDE. Forces the curve label to appear near the end of the curve. Particularly useful when the curve line has a spiral shape.

Interaction: For this option to take effect, the CURVELABEL= option must also be specified.

Interaction: The AUTO setting is not supported if CURVELABELLOCATION=INSIDE is specified. The START and END settings are not supported if CURVELABELLOCATION=OUTSIDE is specified.

Interaction: This option is used in conjunction with the CURVELABELLOCATION= option to determine where the curve label appears. For more information, see Location and Position of Curve Labels.

DATATRANSPARENCY=number

specifies the degree of the transparency of the loess curve.

Default: 0

Range: 0 (opaque) to 1 (entirely transparent)

GROUP=column | expression

creates a distinct set of curves from just the observations that correspond to each unique group value of the specified column.

Default: Each distinct group value might be represented in the graph by a different combination of color and line pattern. Line colors vary according to the GraphData1:ContrastColor - GraphDataN:ContrastColor style references, and line patterns vary according to the GraphData1:LineStyle - GraphDataN:LineStyle style references.

Restriction: The input data must be sorted by the GROUP= column.

Interaction: The group values are mapped in the order of the data, unless the INDEX= option is used to alter the default sequence of line colors and line patterns.

The LINEATTRS= option can be used to override the representations that are used to identify the groups. For example, LINEATTRS=(PATTERN=SOLID) can be used to assign the same pattern to all of the loess curves, letting the line color distinguish group values. Likewise, LINEATTRS=(COLOR=BLACK) can be used to assign the same color to all of the curves, letting the line pattern distinguish group values.

INDEX=positive-integer-column | expression

specifies indices for mapping line attributes (color and pattern) to one of the GraphData1 - GranphDataN style elements.

Default no default

Interaction: For this option to take effect, the GROUP= option must also be specified.

Interaction: All of the indexes for a specific group value must be the same. Otherwise, the results are unpredictable.

Interaction: If this option is not used, then the group values are mapped in the order of the data.

Interaction: The index values are 1-based indices. For the style elements in GraphData1 - GraphDataN, if the index value is greater than N, then a modulo operation remaps that index value to a number less than N to determine which style element to use.

Discussion: Indexing can be used to collapse the number of groups that are represented in a graph. For more information, see Remapping Groups for Grouped Data.

LEGENDLABEL= "string"

specifies a label to be used in a legend.

Default: The string specified on the NAME= option.

Interaction: If the GROUP= option is specified, this option is ignored.

LINEATTRS=style-element | style-element (line-options) | (line-options)

specifies the attributes of the loess curve. See General Syntax for Attribute Options for the syntax on using a style-element and Line Options for available line-options.

Default: The GraphFit style element.

NAME="string"

assigns a name to a plot statement for reference in other template statements.

Default: no default

Restriction: The string is case sensitive, cannot contain spaces, and must define a unique name within the template.

Interaction: The string is used as the default legend label if the LEGENDLABEL= option is not used.

The specified name is used primarily in legend statements to coordinate the use of colors and line patterns between the graph and the legend.

PRIMARY=boolean

specifies that the data columns for this plot and the plot type be used for determining default axis features.

Default: FALSE

Restriction: This option is ignored if the plot is placed under a GRIDDED or LATTICE layout block.

Details: This option is needed only when two or more plots within an overlay-type layout contribute to a common axis. For more information, see When Plots Share Data and a Common Axis

TIPFORMAT=(role-format-list)

specifies display formats for tip columns.

Default: The column format of the variable assigned to the role or BEST6. if no format is assigned to a numeric column.

(role-format-list)

a list of role-name = format pairs separated by blanks.

TIPFORMAT=(Y=6.2)

Requirement: To generate tooltips, you must include an ODS GRAPHICS ON statement that has the IMAGEMAP option specified, and write the graphs to the ODS HTML destination.

The columns assigned to the X, Y, and GROUP (if assigned) roles are automatically included in the tooltip information.

TIPLABEL=(role-label-list)

specifies display labels for tip columns.

Default: The column label or column name of the variable assigned to the role.

(role-label-list)

a list of role-name = "string" pairs separated by blanks.

   TIPLABEL=(Y="Loess Fit")

Requirement: To generate tooltips, you must include an ODS GRAPHICS ON statement that has the IMAGEMAP option specified, and write the graphs to the ODS HTML destination.

The columns assigned to the X, Y, and GROUP (if assigned) roles are automatically included in the tooltip information.

XAXIS=X | X2

specifies whether data are mapped to the primary X (bottom) axis or to the secondary X2 (top) axis.

Default: X

Interaction: The overall plot specification and the layout type determine the axis display for the specified axis. For more information, see How Axis Features are Determined.

YAXIS=Y | Y2

specifies whether data are mapped to the primary Y (left) axis or to the secondary Y2 (right) axis.

Default: Y

Interaction: The overall plot specification and the layout type determine the axis display for the specified axis. For more information, see How Axis Features are Determined.