topic Re: Reversing string in SAS Programming

Reversing string

Neeta — Wed, 13 Jan 2016 18:05:30 GMT

Hi,

I'm a SAS newbie. I was trying out something to reverse the string. I know there is SAS function REVERSE but I want to write my own code for fun 🙂

here is my code

data try;
name="Bellevue";
length revname $ 20;
retain revname;
do i= length(name) to 1 by -1;
revname=catx(revname, strip(substr(name, i, 1)));
output;
end;

run;

but if you run the code, I'm not getting string though I've used retain statement. Whats going wrong?

Re: Reversing string

mohamed_zaki — Wed, 13 Jan 2016 18:18:05 GMT

Chk this old thread

Reverse any string without using function

You do not need retain for that....

Re: Reversing string

Astounding — Wed, 13 Jan 2016 18:26:16 GMT

Several items to note:

As was already mentioned, you don't need RETAIN at all.
OUTPUT should also be removed. Using it creates multiple observations from the original single observation.
CATX is the wrong function. It looks like it should be CATS instead.
Your original value for NAME does not contain any trailing blanks. This becomes a much trickier problem if trailing blanks are involved.
The STRIP function isn't doing anything and therefore should be removed.

Re: Reversing string

FreelanceReinh — Wed, 13 Jan 2016 18:46:28 GMT

Good points from @Astounding. Regarding trailing blanks, I don't think they would be desired as leading blanks in variable REVNAME (and they wouldn't occur as such with the current approach). But if they were desired, one could create them easily with a final revname=right(revname);.

Re: Reversing string

Reeza — Wed, 13 Jan 2016 18:47:40 GMT

Retain is for keeping values as you move down a column or through the data set. Since you're not stepping through a traditional data set and operating on the same line the Retain function isn't required.

Re: Reversing string

PGStats — Thu, 14 Jan 2016 03:52:21 GMT

Here is another approach, using a temporary array

data try;
length name revname $ 20;
array c{100} $1 _temporary_;
do name = "Bellevue", "stressed";
    call missing(of c{*});
    do i= 1 to length(name);
        c{dim(c)-i+1} = char(name,i);
        end;
    revname=cats(of c{*});
    output;
    end;
drop i;
run;

proc print noobs data=try; run;