Automating repetitive tasks is one of SAS©'s great strengths, especially for processing large-scale surveys. However, passing parameters—such as labels or formats—inside a macro is a frequent source of syntax errors.
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Dans : macro SAS9
Note :
The Need: Automate PROC FREQ with Metadata
The user wants to create a %f_freq macro to generate frequency tables. The requirements are specific:
The output must be a data table (OUT=).
The variable must be formatted (grouping of values).
A specific (often long) label must be assigned to the variable in the output table, defined beforehand via a %LET statement.
The problematic code:
The Need: Automate PROC FREQ with Metadata
The user wants to create a %f_freq macro to generate frequency tables. The requirements are specific:
The output must be a data table (OUT=).
The variable must be formatted (grouping of values).
A specific (often long) label must be assigned to the variable in the output table, defined beforehand via a %LET statement.
The problematic code:
| 1 | %let Q1_label='Texte très long pour la question 1...'; |
| 2 | |
| 3 | %macro f_freq(var, var_w, var_label); |
| 4 | PROC FREQ DATA=clean_data order=freq; |
| 5 | TABLE &var / out=freqout.freq_&var; |
| 6 | FORMAT &var &var_w; |
| 7 | label &var=&var_label; /* Assigne le label */ |
| 8 | RUN; |
| 9 | %mend; |
| 10 | |
| 11 | /* L'appel qui ne fonctionne pas comme prévu */ |
| 12 | %f_freq(Q1, Q1_w., Q1_label); |
Note :
The Error: Macro Variable Resolution (&)
As pointed out in the forum response, the error is not in the macro definition, but in its call.
The user wrote: %f_freq(Q1, Q1_w., Q1_label);
The problem: SAS© literally interprets the third parameter as the text "Q1_label". Consequence: In the procedure, SAS© tries to execute label Q1 = Q1_label;, which assigns the text "Q1_label" as the label, instead of the text contained in the variable (the "Very long text...").
The solution: You must use the & (ampersand) sign to tell SAS© to resolve the variable before sending it to the macro.
The Error: Macro Variable Resolution (&)
As pointed out in the forum response, the error is not in the macro definition, but in its call.
The user wrote: %f_freq(Q1, Q1_w., Q1_label);
The problem: SAS© literally interprets the third parameter as the text "Q1_label". Consequence: In the procedure, SAS© tries to execute label Q1 = Q1_label;, which assigns the text "Q1_label" as the label, instead of the text contained in the variable (the "Very long text...").
The solution: You must use the & (ampersand) sign to tell SAS© to resolve the variable before sending it to the macro.
| 1 | /* Appel corrigé */ |
| 2 | %f_freq(Q1, Q1_w., &Q1_label); |
| 3 |
The Impact of Formats and Labels on PROC FREQ
The expert who responded raises an interesting technical point: "I think the format and the label are used for display... I don't think they affect the aggregation."
It is important to clarify this behavior in SAS©:
Formats (
FORMAT): They do affect aggregation. If you apply a format that groups values (for example, transforming 1, 2, 3 into "Small"),PROC FREQwill calculate the frequency for "Small". This is essential for on-the-fly recoding.Labels (
LABEL): They do not affect the calculation, but they are crucial for metadata. TheLABELstatement inside the procedure does indeed allow storing the variable's description in the output table (OUT=).
Note :
Debugging Best Practices
To avoid this kind of confusion between a variable's name and its content, here are two tips from the discussion:
Use %PUT: Before running a complex procedure, display the values in the Log to check what the macro is actually receiving.
Debugging Best Practices
To avoid this kind of confusion between a variable's name and its content, here are two tips from the discussion:
Use %PUT: Before running a complex procedure, display the values in the Log to check what the macro is actually receiving.
| 1 | %macro f_freq(var, var_w, var_label); |
| 2 | %put NOTE: La variable est &var; |
| 3 | %put NOTE: Le label reçu est &var_label; |
| 4 | /* ... reste du code ... */ |
| 5 | %mend; |
Beware of Quotes: If your label already contains quotation marks (as defined in %let Q1_label='...'), make sure not to add extra ones in the label &var=&var_label; statement.
Writing macros requires particular rigor regarding variable scope. Always remember: if you want to pass the content of a variable defined by a %LET statement, you must use the & prefix in the call.
Wichtiger Haftungsausschluss
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