topic Re: Explain do loops in SAS Programming

Explain do loops

vatemro — Thu, 22 Oct 2015 10:08:05 GMT

Please can someone explain in details the data steps below and what each data statement is doing.

thanks

data work.invest;

do year = 2010 to 2014;

capital + 3000;

capital + (capital * 0.10);

end;

Re: Explain do loops

RW9 — Thu, 22 Oct 2015 10:23:51 GMT

The do loop repeats the code within the block the number of times specified by the from and to (and step if supplied).

data work.invest;

do year = 2010 to 2014;

capital + 3000;

capital + (capital * 0.10);

end;

In your instance, the loop variable year runs from 2010 to 2014 (default step 1), so 2010, 2011, 2012, 2013.

You can expand the code to look like:

year=2010

add 3000 to capital

add capital multiplied by 0.10 to capital

year=2011

add 3000 to capital

add capital multiplied by 0.10 to capital

...

So year will end up as 2014, and capital will be the end result of those adds.

Re: Explain do loops

Patrick — Thu, 22 Oct 2015 10:26:56 GMT

Is this an interview or study question?

Do you know SAS Language at all? Which bit of the code is not clear to you?

Here the documentation for a do-loop:

https://support.sas.com/documentation/cdl/en/lestmtsref/68024/HTML/default/viewer.htm#p1cydk5fq0u4bfn1xfbjt7w1c7lu.htm

Another good way to understand what's happening is to actually execute the code, look at the result and try to understand what's going on. Each "output" statement in below code will write a row to table "work.invest".

data work.invest;
  do year = 2010 to 2014;
    output;
    capital + 3000;
    output;
    capital + (capital * 0.10);
    output;
  end;
run;

Re: Explain do loops

vatemro — Thu, 22 Oct 2015 10:34:27 GMT

Am new to programming and am not sure about a lot of the statements. Thanks for your help

Re: Explain do loops

vatemro — Thu, 22 Oct 2015 10:35:30 GMT

Thanks for your help. The explanation was very simplified and clear