Sample 49251: How to find the nth BY group within a data set
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This sample contains two versions of the FIND_BY_GROUP macro.
The first version of the macro enables you to select the nth BY group from the data set. A parameter value of 'Last' enables you to extract the last BY group from the data set.
The second example enables you to select a random BY group from the data set.
These sample files and code examples are provided by SAS Institute Inc. "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Recipients acknowledge and agree that SAS Institute shall not be liable for any damages whatsoever arising out of their use of this material. In addition, SAS Institute will provide no support for the materials contained herein.
This macro enables you to select the nth BY group from the data set. A parameter value of 'Last' enables you to extract the last BY group from the data set.
The second example enables you to select a random BY group from the data set.
data a;
input x $ y;
datalines;
aaa 1
aaa 2
aaa 3
bbb 4
bbb 5
ccc 5
ccc 6
ccc 7
ccc 8
;
%macro find_by_group(n);
%if %UPCASE(&n) ne LAST %then %do;
data _null_;
set a;
by x;
if first.x then n+1;
if n=&n then do;
call execute('data b; set a(where=(x="'||strip(x)||'"));run;');
stop;
end;
run;
%end;
%else %do;
data _null_;
set a end=last;
if last then do;
call execute('data b; set a(where=(x="'||strip(x)||'"));run;');
stop;
end;
run;
%end;
proc print data=b;run;
%mend;
/* in this example, the input data set has 3 possible BY groups. */
/* the parameter value can range from 1 to 3. */
/* if you would like to find the last by group pass in 'last' */
/* (without the quotes) as the value of the paramter N. */
%find_by_group(2)
%find_by_group(1)
%find_by_group(last)
/* this example enables you to randomly extract a by group from a */
/* data set. */
%macro find_by_group;
data _null_;
set a end=last;;
by x;
if first.x then n+1;
if last then call symputx('n',n);
run;
%let by=%sysfunc(int(%sysevalf(%sysfunc(ranuni(0))*&n)));
data _null_;
set a;
by x;
if first.x then n+1;
if n=&by then do;
call execute('data b; set a(where=(x="'||strip(x)||'"));run;');
stop;
end;
run;
proc print data=b;run;
%mend;
%find_by_group
These sample files and code examples are provided by SAS Institute Inc. "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Recipients acknowledge and agree that SAS Institute shall not be liable for any damages whatsoever arising out of their use of this material. In addition, SAS Institute will provide no support for the materials contained herein.
This macro enables you to select the nth BY group from the data set. A parameter value of 'Last' enables you to extract the last BY group from the data set.
The second example enables you to select a random BY group from the data set.
| Type: | Sample |
| Date Modified: | 2013-03-08 14:08:14 |
| Date Created: | 2013-02-22 14:45:49 |
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