Macro

Extract common words from two strings

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Difficulty Level
Beginner
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The `mf_wordsInStr1andStr2` macro takes two parameters, `Str1` and `Str2`, which are character strings. It compares the words in `Str1` with those in `Str2` and builds a new string containing only the words present in both strings. The comparison is case-sensitive. If one of the strings is empty, the macro displays a message in the log and returns nothing.
Data Analysis

Type : INTERNAL_CREATION

The macro processes character strings provided as parameters. It does not read or write traditional or external SAS data.

1 Code Block
MACRO
Explanation :
Definition of the `mf_wordsInStr1andStr2` macro with its input parameters `Str1` and `Str2`. Declaration of local macro variables used for word counting, loops, storing extracted words, and the final result.
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1%macro mf_wordsInStr1andStr2(
2 Str1= /* string containing words to extract */
3 ,Str2= /* used to compare with the extract string */
4)/*/STORE SOURCE*/;
5 
6%local count_base count_extr i i2 extr_word base_word match outvar;
2 Code Block
MACRO
Explanation :
This block checks if one of the input strings (`Str1` or `Str2`) is empty. If so, a message is displayed in the SAS log indicating the string values, and the macro terminates (`%return`) without producing any output.
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1%IF %LENGTH(&str1)=0 or %LENGTH(&str2)=0 %THEN %DO;
2 %put base string (str1)= &str1;
3 %put compare string (str2) = &str2;
4 %return;
5%END;
3 Code Block
MACRO
Explanation :
Use of the `%sysfunc(countw(...))` macro function to count the number of words in each input string (`Str1` and `Str2`) and store these counts in the `count_base` and `count_extr` macro variables.
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1%let count_base=%sysfunc(countw(&Str2));
2%let count_extr=%sysfunc(countw(&Str1));
3 
4 Code Block
MACRO
Explanation :
Outer loop (`%do i=1 %to &count_extr;`) to iterate through each word in `Str1`. For each word (`extr_word`), an inner loop (`%do i2=1 %to &count_base;`) iterates through all words in `Str2`. If a match is found (`&extr_word=&base_word`), the `match` variable is set to 1. If `match` is 1 after the inner loop, the word (`extr_word`) is added to the `outvar` macro variable, which accumulates the result.
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1%DO i=1 %to &count_extr;
2 %let extr_word=%scan(&Str1,&i,%str( ));
3 %let match=0;
4 %DO i2=1 %to &count_base;
5 %let base_word=%scan(&Str2,&i2,%str( ));
6 %IF &extr_word=&base_word %THEN %let match=1;
7 %END;
8 %IF &match=1 %THEN %let outvar=&outvar &extr_word;
9%END;
5 Code Block
MACRO
Explanation :
The macro returns the value of the `outvar` macro variable, which contains all common words found in `Str1` and `Str2`, separated by spaces. `%mend` marks the end of the macro definition.
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1 &outvar
2 
3%mend mf_wordsInStr1andStr2;
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Copyright Info : Copyright (c) 2001-2006 Rodney Sparapani (from _version.sas); Copyright © 2022, SAS Institute Inc. (from print_macro_parameters.sas); Copyright 2010-2023 HMS Analytical Software GmbH (from macro_without_brief_tag.sas, _delfile.json, _issuewarningmessage.json); Allan Bowe (mentioned in the HELP START/END block as a general reference).


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