Replace missing by median values within each case

 

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/************************************************.
* Syntax to replace missing values in a case 
by the median of the non missing values.
Raynald Levesque rlevesque@videotron.ca
************************************************/.

* Warnings are reported when a case has no missing values (because the 
RMV command cannot do its job). Of course, these warnings are to be ignored.

SET MPRINT=on.

* Define dummy data file for illustration purposes.
NEW file.
INPUT PROGRAM.
SET SEED=98675423.
VECTOR q(8F8.2).
LOOP id=1 TO 25.
	LEAVE id.
	LOOP #cnt=1 TO 8. 	
*		say about 10% of answers should have missing value. 		
		IF UNIFORM(1)<.9 q(#cnt)=1+TRUNC(UNIFORM(9)).
	END LOOP.
	END CASE.
END LOOP.
END FILE.
END INPUT PROGRAM.
EXECUTE.
LIST.

*assume without loss of generality that all data are numeric.
*if this is not the case: 
*	save the Numeric Columns you are interested in a file NC along with the numeric case id.
*	delete the NC from you main file and save the resulting file as FILEB.
*	apply the following code to the file containing the NC.
*	merge the resulting file with FILEB. 

*Construct the variable names to be used after the FLIP.
STRING nnames(A8).
COMPUTE cn=$casenum.
COMPUTE nnames=CONCAT('v',LTRIM(STRING(cn,F6.0))).
EXECUTE.

* Define a macro which will replace the missing values.

*/////////////////////////////////////////////////////.
DEFINE !doit (nbvar=!TOKENS(1)).
FLIP /NEWNAMES=nnames.
VECTOR !CONCAT('r(',!nbvar,'F8)').

SUMMARIZE
  /TABLES=v1 TO !CONCAT(v,!nbvar)
  /FORMAT=NOLIST TOTAL
  /TITLE='Print Medians for checking purposes'
  /MISSING=VARIABLE
  /CELLS=MEDIAN .

!DO !cnt=1 !TO !nbvar 
RMV !CONCAT(r,!cnt) = MEDIAN(!CONCAT(v,!cnt,',ALL)').
!DOEND

MATCH FILES FILE=* /KEEP=case_lbl r1 TO  !CONCAT(r,!nbvar).
FLIP.
*### in next line 8 is the number of variables in initial file. 
MATCH FILES FILE=* /KEEP=q1 TO  q8 id.
!ENDDEFINE.
*/////////////////////////////////////////////////////.

*### in next line 25 is the number of cases in the original file.
!doit nbvar=25.
LIST.
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