reading a data set multiple times in SAS - loops

Question

I am new here. I am trying to read in a data set multiple times. so for example, assume that I have 3 observations in a data set (called tempfile) for a variable called temp. the three observations are 4,6, and 5.. so I want to read in the set x number of times so the 4th observation would be 4, fifth would be 6 and sixth, would be 5. the 7th would be 4, etc etc. I have tried this literally a few dozen ways, by doing something like
data new;
do i=1 to 100;
set tempfile;
end;
output;
run;
I have tried this by moving the do statement, moving the output statement, omitting the output statement..... every which way, trying macros also. can somebody help? thanks John
followup....
Hello:
Thanks for response. That did work. I would like to now do several things involving some “if then” statements inside the loop (more than just reading in the data set).
I want to read in a data set n number of times, and each time, there will be two if then statements
So, assume I read in 3 numbers any number of times; 7, 15, and 12
As each number is read, it will ask if it is less than 10. And each time it will create a random number.
If less than 10, then
If rand(uniform) < .4 then 1 is added to counter1, else 1 is added to counter2
And if >= 10,
Then
If rand(uniform) < .2 then 1 is added to counter1, else 1 is added to counter2
Any help is much appreciated.
Thanks
John

Answer 1

The way that most data steps actually stop is when SAS reads past the end of the input. So you need a method that prevents SAS from doing that.
The easiest way to replicate the data is to just execute multiple output statements. So the first record is repeated three times, then the second record is repeated three times, etc.
data want;
set tempfile ;
do i=1 to 3;
output;
end;
run;
Another method is to just list the dataset multiple times on the SET statement. So to read it in 3 times just use
data want;
set tempfile tempfile tempfile;
run;
You could probably use macro logic or even just a macro variable to make the number of repetitions variable.
data _null_; call symputx('list',repeat('tempfile ',3-1)); run;
data want; set &list; run;
Other method is to use the POINT= and NOBS= options on the SET statement so that SAS never reads past the end and you can jump back to the beginning. But since it never reads past the end of the input data you will need to manually tell it when to stop.
data want ;
do i=1 to 3;
do p=1 to nobs ;
set tempfile point=p nobs=nobs;
output;
end;
end;
stop;
run;
Or more in the spirit of your original post you might want to use the MOD() function to figure out which observation to read next.
data want;
if _n_ > 100 then stop;
p=1+mod(_n_-1,nobs);
set tempfile point=p nobs=nobs;
run;

Answer 2

If you have SAS/STAT software SURVEYSELECT.
data have;
do temp=4,6,5;
output;
end;
run;
proc surveyselect reps=10 rate=1 out=temp2 noprint;
run;

Answer 3

The data step is designed for serial processing. In this case, you need to "remember" previous observations. You can do it using only the data step, but for that use case, there are other solutions in the SAS environment that are simpler. The one I suggest is a macro that appends the original file n times:
%macro replicate( data=, out=, n=)/des='&out is &data repeated &n times.';
data &out;
set
%do i=1 %to &n;
&data
%end;
; /* This ; ends the data step `set` statement */
run;
%mend;
You could test your example with this helper:
%macro test;
data have; /* create the example data set */
temp = 4; output;
temp = 6; output;
temp = 5; output;
run;
%replicate( data=have, out=want, n=4 );
proc print; quit;
%mend;
Here is a portion of the SAS doc that adds lots of detail with many examples.