topic Re: DO loop troubles in SAS Programming

DO loop troubles

GKati — Fri, 16 Mar 2018 11:31:18 GMT

Hi,

I have a simple do-loop:

data nobs;

do i=i to 2;

data nobs_i;

set nobs_i;

keep Nobsused;

end;

run;

It is giving me the following error msg: No Matching DO/SELECT statement. Why?

Re: DO loop troubles

Kurt_Bremser — Fri, 16 Mar 2018 11:50:16 GMT

The second data statement begins a new data step, so the do in the old one has no matching end. What are you trying to do?

Re: DO loop troubles

GKati — Fri, 16 Mar 2018 14:04:09 GMT

I'm trying to figure out do-loops with a simple example. I have two datasets: nobs_1 and nobs_2. I would like to keep Nobsused in both datasets. Thanks

Re: DO loop troubles

Kurt_Bremser — Fri, 16 Mar 2018 14:10:12 GMT

The basic step would be

data nobs;   
set
  nobs_1
  nobs_2
;
keep Nobsused;
run;

If you have an arbitrary number of datasets, use

set
  nobs_1-nobs_&n.
;

if your number of datasets is stored in macro variable n.

Re: DO loop troubles

GKati — Fri, 16 Mar 2018 14:25:54 GMT

Ok, this is helpful. But what if I wanted to keep the two datasets separete?

Re: DO loop troubles

Reeza — Fri, 16 Mar 2018 14:43:10 GMT

Back to the original question then, what are you trying to accomplish here?

@GKati wrote:
Ok, this is helpful. But what if I wanted to keep the two datasets separete?

Re: DO loop troubles

GKati — Fri, 16 Mar 2018 14:50:52 GMT

I'm trying to figure out do-loops with a simple example. I have two datasets: nobs_1 and nobs_2. I would like to keep Nobsused in both datasets without merging the two datasets.

I am going to have about 16 different datasets that I need to modify. I need to keep them separately and run a code through them one-by-one.
Thanks

Re: DO loop troubles

Reeza — Fri, 16 Mar 2018 14:59:02 GMT

What is NObsUsed?

@GKati wrote:
I'm trying to figure out do-loops with a simple example. I have two datasets: nobs_1 and nobs_2. I would like to keep Nobsused in both datasets without merging the two datasets.

I am going to have about 16 different datasets that I need to modify. I need to keep them separately and run a code through them one-by-one.
Thanks

Re: DO loop troubles

GKati — Fri, 16 Mar 2018 15:03:43 GMT

It's variable.

Re: DO loop troubles

Reeza — Fri, 16 Mar 2018 15:12:24 GMT

I'm not a fan of twenty questions. Please explain your process in detail.

The approach you're currently trying doesn't make sense for any process.

@GKati wrote:
It's variable.

Re: DO loop troubles

gamotte — Fri, 16 Mar 2018 15:21:36 GMT

Hello,

If you goal is to understand do loops, you should start by looking at examples of its usage rather than trying to guess how they work.

Do loops are used inside data steps and not to iterate on several data steps, procs,...

If you are interested in code generation you should learn SAS macro language but a minimal command of the base language is required to avoid confusion.

Re: DO loop troubles

GKati — Fri, 16 Mar 2018 15:26:07 GMT

gamotte, Reeza

Thanks for your help. My intention was not to waste your time. I have been looking at do-loop examples and that is how I came up with the code above. My intuition comes from STATA, where it is possible to loop over different datasets and modify them without merging them. I now understand that that is not possible in SAS and that I need to write a macro to do that. I will try that and see how I do.
Thanks for your time.

Re: DO loop troubles

Reeza — Fri, 16 Mar 2018 15:38:40 GMT

If you state what you're trying to achieve we can recommend the best method.

For example, PROC DATASETS is more efficient to modify data sets to drop/keep variables that multiple data steps. If you take the approach used in other programming languages and try and apply them to another language, you miss learning how to efficiently use the new language.

Or that you can easily create a view with just the one variable that only gets created when called.

@GKati wrote:
gamotte, Reeza

Thanks for your help. My intention was not to waste your time. I have been looking at do-loop examples and that is how I came up with the code above. My intuition comes from STATA, where it is possible to loop over different datasets and modify them without merging them. I now understand that that is not possible in SAS and that I need to write a macro to do that. I will try that and see how I do.
Thanks for your time.