i have a file of students and each student can appear more than once in it.
student score
100 A
100 B
100 C
101 A
101 B
102 A
103 B
103 A
103 C
.......
.........
i need to randomly select maximum to 2 records per student
Any idea how to achieve this guys please? 🙂
I think this might get you started. Since you may have some students with only one score if we want to use surveyselect which is designed for random sampling we need to describe how many records to pull for each student so the Proc Freq and Data step create a record for each student and if they only have one score then you get one requested, otherwise 2. Note that the output dataset from Surveyselect, Want, will have additional variables that can be used for weighting and tell what the probability of selection was.
proc freq data=have noprint;
tables student/list out=temp;
run;
data samplesize;
set temp;
if count > 1 then _nsize_ = 2;
else _nsize_ = 1;
run;
proc surveyselect data=have out=want
sampsize=samplesize ;
strata student;
run;
I think this might get you started. Since you may have some students with only one score if we want to use surveyselect which is designed for random sampling we need to describe how many records to pull for each student so the Proc Freq and Data step create a record for each student and if they only have one score then you get one requested, otherwise 2. Note that the output dataset from Surveyselect, Want, will have additional variables that can be used for weighting and tell what the probability of selection was.
proc freq data=have noprint;
tables student/list out=temp;
run;
data samplesize;
set temp;
if count > 1 then _nsize_ = 2;
else _nsize_ = 1;
run;
proc surveyselect data=have out=want
sampsize=samplesize ;
strata student;
run;
thanks ballardw
works perfectly
interesting approach
thx again
The SELECTALL option provides a simplier solution. No counting required.
data student;
input (student score)($);
cards;
100 A
100 B
100 C
101 A
101 B
102 A
103 B
103 A
103 C
;;;;
run;
proc print;
run;
proc surveyselect data=student seed=4354 n=2 out=sample2 selectall;
strata student;
run;
proc print;
run;
Good point @data_null__ I wish I could say that I was providing a more general solution where you had different selection rules based on counts within strata. But I just forgot the SELECTALL option as none of my stratified data gets close to the using all of the records in a stratum.
this is even shorter.
Thanks Data_Null, thanks guys
Build your skills. Make connections. Enjoy creative freedom. Maybe change the world. Registration is now open through August 30th. Visit the SAS Hackathon homepage.
Register today!Learn the difference between classical and Bayesian statistical approaches and see a few PROC examples to perform Bayesian analysis in this video.
Find more tutorials on the SAS Users YouTube channel.
Select SAS Training centers are offering in-person courses. View upcoming courses for: