topic Re: DO Loop in New SAS User

DO Loop

nishSAS — Wed, 13 Feb 2019 09:26:01 GMT

Hello,

I am trying to create edit existing variable values with the help of DO LOOP in SAS Data Step. Below is the code i have written for the same. But when i am running this code I am not getting the expected result. What is going wrong in my code can you please suggest the corrections

data IN;
set IN;
do x = 1 to 20;/*Update the Range if fill Number Value goes beyond 20*/
y = x - 1;
if fill_Number = x then fill_Number = y;
else fill_Number = x;
end;
run;

Please correct me if my code is wrong.

Thanks

Re: DO Loop

PeterClemmensen — Wed, 13 Feb 2019 09:31:58 GMT

What goes wrong? What do you expect and what results do you get?

Re: DO Loop

Kurt_Bremser — Wed, 13 Feb 2019 09:52:23 GMT

data out;
/* it is never a good idea to overwrite the incoming dataset */
/* if something bad happens, all work up to now is lost */
set in;
do x = 1 to 20;/*Update the Range if fill Number Value goes beyond 20*/
  y = x - 1;
  if fill_Number = x
  then fill_Number = y;
  else fill_Number = x;
end;
run;

The way your code is written, fill_number will ALWAYS end up as 20.

Re: DO Loop

RW9 — Wed, 13 Feb 2019 09:55:00 GMT

Post test data in the form of a datastep so we can see the inputs. Show what output should be from that data. We cannot guess from nothing.

Generally a do loop iterates only within the individual observations, so in this case, for each observation the do loop will run 20 times, setting y to loop iteration -1, and when that equals x then the variable fill_number becomes the value in y, otherwise fill_number becomes x. So from that logic you can see that the logic is never going to be right. Take an example:

loop 1: fill_number=0, x=1, y=x-1=0, fill_number set to 0

loop 2: fill_number=0, x=2, y=x-1=1, fill_number set to 2

loop 3: fill_number=2, x=3, y=x-1=2, fill_number set to 2

loop 4: fill_number=2, x=4, y=x-1=3, fill_number set to 3

...

As I can't see what you wanted to achieve i can't tell if that is right or "not working".

Re: DO Loop

nishSAS — Wed, 13 Feb 2019 12:32:36 GMT

Thanks Kurt for your reply.

I wanted to edit the fill_number column where column value start with 1 it should become 0, if value is 2 it should become 1 and so on.

When i am running below code my all fill_numver values are becoming 20. Which i don't want.

Re: DO Loop

Kurt_Bremser — Wed, 13 Feb 2019 12:37:06 GMT

That means

fillnumber = fillnumber - 1;

For further help, post example data in a data step with datalines, and the expected output. See my footnotes for advice.