SAS Macro Programs: meanplot

The meanplot macro ( get meanplot.sas)

Plot means for factorial designs

For a 3-factor design, if the factors are A, B, C, the macro, by default, uses variable A as the horizontal(XVAR =) variable in the plots, plots separate curves for each value of variable B, and produces separate panels for each level of variable C, as well as one additional panel for the average of means over variable C. You can obtain different views of the means by reordering the CLASS= variables, or assigning variables to particular roles with the XVAR=, CVAR=, and PANELS= arguments.

Version 1.3 provides an ADJUST= parameter to give true confidence-interval error bars, possibly adjusted for multiple comparisons using the Bonferroni or Tukey studentized range procedures. The error bar lengths are calculated as one-half the width of the confidence interval for the difference between two means in a given effect. Therefore, the error bars for two means in a given effect will overlap iff those means do not differ at the specified ALPHA= value. When sample sizes are unequal for any effect, the macro uses the geometric mean of the sample sizes for that effect as a common value in the calculation of the adjusted error bar lengths. The Tukey adjustment uses the PROBMC function, and works only in SAS Version 6.09 or later.

Method

Usage

The arguments may be listed within parentheses in any order, separated by commas. For example:

   %meanplot(data=recall, response=score, class=Group Gender Order);

   %panels(rows=1, cols=4);

   goptions nodisplay;
   %meanplot(data=recall, response=score, class=Group Gender Order);
   goptions display;
   %panels(rows=1, cols=4);

Arguments

DATA=

The name of the SAS dataset to be plotted. If DATA= is not specified, the most recently created data set is used.

RESPONSE=

Name of the response (dependent) variable in the input data set. Must be numeric.

CLASS=

The names of 1-3 factor variables, separated by spaces.

FREQ=

An optional frequency variable. Each observation is treated as if it were repeated as many times as the value of the FREQ= variable. Observations with a FREQ= value less than or equal to 1 are omitted from the calculation. Fractional values are not allowed.

You must specify the FREQ= variable when input comes from summary data (means, standard deviations) processed by the %stat2dat macro.

XVAR=

Name of the factor variable to be used as the horizontal variable in plots. If XVAR= is not specified, the first CLASS= variable is used.

CVAR=

Name of the factor variable to be used as the curve variable in plots. If CVAR= is not specified, the second CLASS= variable is used in 2-way and 3-way plots.

PANELS=

Name of the factor variable to be used to define multiple panels in plots. If PANELS= is not specified, the third CLASS= variable is used in 3-way plots.

PFMT=

Format for the PANELS= variable. The default is BEST. if the panels variable is numeric, and $16. otherwise.

CMEAN=

Specifies whether an additional curve, representing the average over the levels of the CVAR= variable, is added to each panel.

Z=

Std. error multiple for confidence intervals or error bars drawn in the GPLOT versions of the plots. The default, Z=1 shows one standard error for each mean plotted. Use Z=1.96 for approximate individual 95% CI, or Z=0 for plots without error bars. The Z= parameter is ignored if you specify an ADJUST= method.

ADJUST=

Specifies whether to calculate confidence-interval error bars, and whether these are adjusted for multiple comparisons. In this case, error bars will overlap iff a given pair of means do not differ significantly. ADJUST=T or LSD provide standard t-value error bars, unadjusted for multiple comparisons; ADJUST=BON provides Bonferroni adjusted error bars for all pairwise comparisons; ADJUST=TUKEY or HSD provides Tukey-test (studentized range) adjustments for all pairwise comparisons..

ALPHA=.05

Specifies the error rate for comparisons made with the ADJUST= option.

PPLOT=

Specifies whether line printer plots are to be done. Default: NO

GPLOT=

Specifies whether high-res plots are to be done. Default: YES

PRINT=

Specifies whether to print the means. Default: YES

Additional options for high-res PROC GPLOT plots

ANNO=

Name of an additional input Annotate data set. If specified, this is appended to the Annotate data set used to draw error bars in the plot.

SYMBOLS=

List of SAS/GRAPH symbols for the levels of the CVAR=variable. There should be as many symbols as there are distinct values of the CVAR=variable.

COLORS=

List of SAS/GRAPH colors (for the GPLOT version) for the levels of the CVAR=variable. There should be as many colors as there are distinct values of the CVAR=variable.

LINES=

List of SAS/GRAPH line styles (for the GPLOT version) for the levels of the CVAR=variable. There should be as many lines as there are distinct values of the CVAR=variable.

HAXIS=

Axis statement for custom horizontal axis, e.g., HAXIS=AXIS2

VAXIS=

Axis statement for custom response axis, e.g., VAXIS=AXIS1. If no axis statement is defined, the program uses AXIS1 LABEL=(a=90).

Error bar calculations may cause some annotations to outside the vertical plot range, producing the message: DATA SYSTEM REQUESTED, BUT VALUE IS NOT IN GRAPH 'Y' To correct this, specify the ORDER= option in an AXIS statement to extend the range of the Y axis suitably, for example: AXIS1 LABEL=(a=90) ORDER=(0 to 30 by 5).

LEGEND=

Legend statement for custom CVAR legend, e.g., LEGEND=LEGEND1 If no legend is specified, the program uses LEGEND1 POSITION=(BOTTOM CENTER INSIDE) OFFSET=(0,1) MODE=SHARE FRAME;

PLOC=

Specifies the location for panel labels identifying the level of the PANEL= variable. Specify two numbers giving the screen coordinates in percent of the left edge of the panel label. The default is PLOC=5 95.

GOUT=

Name of output graphics catalog.

Features

• The program does not specify the heights or fonts for any labels in the plots. You should use the GOPTIONS HTEXT= FTEXT= options to define these.
• Variables are labelled in the plots using their variable label if a label has been defined in the input data set; otherwise, the variable name is used as the variable label.
• Plots for the mean of the curve variable are labelled according to the convention of PROC SUMMARY, where a missing value (. for numeric and ' ' for character variables) represents the fact that that variable has been averaged over. Thus, a panel which represents the means of factors A and C averaged over factor B will be labelled 'B = .' or 'B ='.
• When your goal is to produce a combined plot showing the panels together you should probably use an empty TITLE statement to suppress the generation of a title in each panel.

Example

data learning;
   do grade = 5,12;
   do words = 'low ', 'high';
   do feedback = 'Control', 'Pos', 'Neg';
      input mean @@;
      output;
      end; end; end;
lines;
8.8 8.0 7.6
8.0 4.4 3.8
9.0 8.4 8.0
7.8 7.4 7.2
;

%stat2dat(data=learning, class=grade words feedback,
   out=raw, mean=mean, n=5, MSE=1.75, depvar=recall);

The three panels are combined using the %panels macro.

%include goptions;
goptions htext=1.8 htitle=2.3;
%meanplot(data=raw,
   freq=freq, 
   response=recall, class=Feedback Words Grade, cmean=NO, ploc=45 95);
   
%panels(rows=1, cols=3, equate=Y);

See also