Drop variables from a SAS data set when all its values are missing...

Drop variables from a SAS data set when all its values are missing…

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/* Create sample data set */

data missing;

input n1 n2 n3 n4 n5 n6 n7 n8 c1 $ c2 $ c3 $ c4 $;

datalines;

1 . 1 . 1 . 1 4 a . c .

1 1 . . 2 . . 5 e . g h

1 . 1 . 3 . . 6 . . k l

;

options symbolgen;

/*Create two macro variables, num_qty and char_qty, to hold*/

/*the number of numeric and character variables, respectively.*/

/*These will be used to define the number of elements in the ARRAYs*/

/*in the next DATA step.*/

data _null_;

set missing (obs=1);

array num_vars[*] _NUMERIC_;

array char_vars[*] _CHARACTER_;

call symputx('num_qty', dim(num_vars));

call symputx('char_qty', dim(char_vars));

run;

data _null_;

set missing end=finished;

/* Use the reserved word _NUMERIC_ to load all numeric variables  */

/* into the NUM_VARS array.  Use the reserved word _CHARACTER_ to */

/* to load all character variables into the CHAR_VARS array.      */

array num_vars[*] _NUMERIC_;

array char_vars[*] _CHARACTER_;

/* Create 'flag' arrays for the variables in NUM_VARS and CHAR_VARS. */

/* Initialize their values to 'missing'.  Values initialized on an   */

/* array statement are retained.                                     */

array num_miss [&num_qty] $ (&num_qty * 'missing');

array char_miss [&char_qty] $ (&char_qty * 'missing');

/* LIST will contain the list of variables to be dropped.  Ensure  */

/* it's length is sufficient.                                      */

length list $ 50;

/* Check for non-missing values.  Reassign the corresponding 'flag' */

/* value accordingly.                                               */

do i=1 to dim(num_vars);

if num_vars(i) ne . then num_miss(i)='non-miss';

end;

do i=1 to dim(char_vars);

if char_vars(i) ne '' then char_miss(i)='non-miss';

end;

/* On the last observation of the data set, if a 'flag' value is still */

/* 'missing', the variable needs to be dropped.  Concatenate the       */

/* variable's name onto LIST to build the values of a DROP statement   */

/* to be executed in another step.                                     */

if finished then do;

do i= 1 to dim(num_vars);

if num_miss(i) = 'missing' then list=trim(list)||' '||trim(vname(num_vars(i)));

end;

do i= 1 to dim(char_vars);

if char_miss(i) = 'missing' then list=trim(list)||' '||trim(vname(char_vars(i)));

end;

call symput('mlist',list);

end;

run;

/* Use the macro variable MLIST in the DROP statement.  PROC DATASETS can */

/* be used to drop the variables instead of a DATA step.                  */

data notmiss;

set missing;

drop &mlist;

run;

proc print;

run; Source http://support.sas.com/kb/24/622.html