Value Match Search and Variable Name Retrieval

The script first generates a table containing ratings. It then compares a target 'rating' column with three agency columns (moodys, s_and_p, fitch). Several techniques are presented: classic IF-ELSE conditions, using the WHICHC function to find the index of the matching column, and an advanced method combining WHICHC, ARRAY, and VNAME to dynamically retrieve the name of the corresponding variable. A final step warns against misalignment between the order of WHICHC arguments and the ARRAY.

Data Analysis

Type : CREATION_INTERNE

Data is generated directly in the code via assignment and OUTPUT statements.

1 Code Block

DATA STEP Data

Explanation :
Creation of the 'ratings' table containing a target 'rating' value and three comparison columns ('moodys', 's_and_p', 'fitch').

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1	DATA ratings;
2	LENGTH rating $4;
3	rating = 'A+';
4	moodys = 'Baa2';
5	s_and_p = 'BBB+';
6	fitch = 'A+';
7	OUTPUT;
8	rating = 'Aa3';
9	moodys = 'Aa3';
10	s_and_p = 'AAA';
11	fitch = 'AA-';
12	OUTPUT;
13	rating = 'c';
14	moodys = 'Aa3';
15	s_and_p = 'AAA';
16	fitch = 'AA-';
17	OUTPUT;
18	rating = 'D-';
19	moodys = 'Aa3';
20	s_and_p = 'D-';
21	fitch = 'D-';
22	OUTPUT;
23	RUN;

2 Code Block

DATA STEP

Explanation :
First matching method using a classic IF-ELSE conditional structure to identify the corresponding column.

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1	DATA ratings_match;
2	SET ratings;
3	LENGTH rating_match $8;
4
5	IF rating = moodys THEN rating_match = 'moodys';
6	ELSE IF rating = s_and_p THEN rating_match = 's_and_p';
7	ELSE IF rating = fitch THEN rating_match = 'fitch';
8	ELSE rating_match = 'no match';
9	RUN;

3 Code Block

DATA STEP

Explanation :
Use of the WHICHC function to return the index (position) of the first matching variable in the provided list.

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1	DATA ratings_match;
2	SET ratings;
3	/* WHICHC talar om variabelnumret man fr trff p, baserat p ordningen
4	man raddar upp variablerna i p samma stt som COALESCEC.
5	Finns bara trff i en variabel spelar ordningen ingen roll.
6	Prioordning (i de fall man fr trff p flera):
7	1. Moodys
8	2. S&P
9	3. Fitch */
10	variable_match_number = whichc(rating, moodys, s_and_p, fitch);
11	RUN;

4 Code Block

DATA STEP

Explanation :
Combination of an ARRAY, the WHICHC function, and the VNAME function. The index returned by WHICHC is used to access the array element, and VNAME retrieves the source variable name.

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1	DATA ratings_match;
2	SET ratings;
3	LENGTH rating_match $8;
4	/* Array fr att peka p de tre variablerna med vrden,
5	mste ha samma ordning som WHICHC */
6	array rating_agency [3] moodys s_and_p fitch;
7
8	variable_match_number = whichc(rating, moodys, s_and_p, fitch);
9
10	/* Fr man trff i ngon variabel g vidare och plocka fram namnet p variabeln */
11	IF variable_match_number THEN rating_match = vname(rating_agency[variable_match_number]);
12	ELSE rating_match = 'no match';
13	RUN;

5 Code Block

DATA STEP

Explanation :
Demonstration of a logical error case: the order of variables in WHICHC differs from the order in the ARRAY, which leads to retrieving the wrong variable name via VNAME.

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1	/* ndrar ordningen p WHICHC och inte arrayen, blir helt tokigt.
2	r det lnga listor kan man med frdel speca ordningen i en
3	makrovariabel s man bara gr det 1 gng. */
4	DATA ratings_match_error;
5	SET ratings;
6	LENGTH rating_match $8;
7	array rating_agency [3] moodys s_and_p fitch;
8
9	variable_match_number = whichc(rating, s_and_p, fitch, moodys);
10
11	IF variable_match_number THEN rating_match = vname(rating_agency[variable_match_number]);
12	ELSE rating_match = 'no match';
13	RUN;

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