Flexible Templates

Expressions and Functions

In the GTL, expressions can be used to compute constants and data columns. The expressions must be enclosed in an EVAL construct. Within the expression you can use DATA step functions, arithmetic operators, and other special functions supported by the GTL.

Expressions are also useful in text statements like ENTRY and ENTRYTITLE. Both of these statements support rich text and have special text commands such as {SUP}, {SUB}, and {UNICODE}, which enable subscripting, superscripting, and Unicode characters.

The following template shows how the

symbol is included in the title line using its hexadecimal Unicode value. Also, new data columns are computed for the upper and lower error bars of the scatter plot, based on the input columns MEANWEIGHT and STDERR.

proc template;
 define statgraph expression;
  begingraph;
  entrytitle "Errorbars show " {unicode "00B1"x} "2 SE";  
   layout overlay;
    scatterplot x=age y=meanweight /
       yerrorlower=eval(meanweight - 2*stderr)
       yerrorupper=eval(meanweight + 2*stderr);
    seriesplot x=age y=meanweight;
   endlayout;
  endgraph;
 end; 
run;

For more information about using expressions, see Expressions. For more information about using functions, see Functions.

Dynamics and Macro Variables

An extremely useful technique for generalizing templates is to define dynamics, macro variables, or both. The dynamics and macro variables resolve when the template is executed. The following PROC TEMPLATE statements can be used in a DEFINE STATGRAPH block:

Template Statement	Purpose	Value supplied by...
DYNAMIC	defines dynamic(s)	either of the following: DYNAMIC= suboption of ODS= option of FILE PRINT DYNAMIC statement of PROC SGRENDER
MVAR	defines macro variable( s)	%LET or CALL SYMPUT( )
NMVAR	defines macro variable( s) that resolves to a number(s)	%LET or CALL SYMPUT( )
NOTES	provides information about the graph definition	user-supplied text

The following example defines a template named DYNAMICS that can create a histogram and density plot for any variable. It defines both macro variables and dynamics for run time substitution. No data-dependent information is hard coded in the template.

Note: You can initialize macro variables with %LET statements and dynamics with SGRENDER’s DYNAMIC statement.

proc template;
 define statgraph dynamics;
   mvar SYSDATE9 SCALE;
   nmvar BINS;
   dynamic VAR VARLABEL;
   begingraph;
     entrytitle "Histogram of " VAR;
     entrytitle "with Normal Distribution"; 
     layout overlay / xaxisopts=(label=VARLABEL);
       histogram VAR /  scale=SCALE  nbins=BINS; 
       densityplot VAR / normal(); 
     endlayout;
     entryfootnote halign=right "Created: " SYSDATE9 /
       textattrs=GraphValueText;
   endgraph;
 end;
run;

%let bins=6;
%let scale=count;
proc sgrender data=sashelp.class 
              template=dynamics;
  dynamic var="Height" varlabel="Height in Inches";
run;

Graph Generated from Template with Dynamics and Macro Variables

For more information about using dynamics and macro variables, see Dynamics and Macro Variables.

Conditional Logic

Using conditional logic, you can create templates that have multiple visual results or output representations, depending on existing conditions. The evaluation of a logical expression must generate one or more complete statements (not portions of statements). All conditional logic uses one of the following constructs:

if ( condition )
  statement(s);
endif;

if ( condition )
  statement(s);
else
  statement(s);
endif;

On the IF statement, condition must be enclosed in parentheses. The condition can be any standard SAS expression involving arithmetic, logical operators, comparison operators, Boolean operators, or concatenation operators. The expression can also use SAS DATA step functions. The expression resolves to a single numeric value, which is true or false.

In the following example, a histogram is conditionally overlaid with a normal distribution curve, a Kernel Density Estimate distribution curve, both, or neither:

proc template;
  define statgraph conditional;     
   dynamic VAR VARLABEL BINS CURVE;
   begingraph;
    entrytitle "Histogram of " VAR;  
    layout overlay / xaxisopts=(label=VARLABEL);
     histogram VAR /  nbins=BINS; 
	  
     if (upcase(CURVE) in ("ALL"  "KERNEL"))
        densityplot VAR / kernel() name="k" 
                          legendlabel="Kernel"
                          lineattrs=(pattern=dash); 
     endif;	 

     if (upcase(CURVE) in ("ALL" "NORMAL"))
        densityplot VAR / normal() name="n" 
                          legendlabel="Normal";
     endif;

     discretelegend "n" "k"; 
   endlayout;
  endgraph;
 end;
run;

Note that the legend syntax does not have to be made conditional. At run time, each plot name in the legend is checked. If the plot does not exist, its name is removed from the legend name list. If no names appear in the DISCRETELEGEND statement, the legend “drops out” and the histogram is resized to fill the remaining space.

For more information about using conditional logic, see Conditional Logic.