topic Re: Drop variables without directly mention them or without DROP statement in SAS Programming

Drop variables without directly mention them or without DROP statement

webart999ARM — Tue, 04 Aug 2020 13:54:15 GMT

Hi there,

Hope guys, you are doing well these days.
I have one simple question.
Yes, it's simple but could not manage to find an appropriate solution 🙂

I have below mentioned 36 variables, and want to drop them in my final data step.

But I think it'll be not accurate with just mention them in the drop statement.

Can anyone suggest another approach?

Thank you in advance

Re: Drop variables without directly mention them or without DROP statement

PaigeMiller — Tue, 04 Aug 2020 13:55:42 GMT

@webart999ARM wrote:

Hi there,

Hope guys, you are doing well these days.
I have one simple question.
Yes, it's simple but could not manage to find an appropriate solution 🙂

I have below mentioned 36 variables, and want to drop them in my final data step.

But I think it'll be not accurate with just mention them in the drop statement.

Can anyone suggest another approach?

What do you mean "not accurate"? Why do you think the DROP statement will not work; the DROP statement does exactly what it is supposed to do.

Re: Drop variables without directly mention them or without DROP statement

PGStats — Tue, 04 Aug 2020 13:56:48 GMT

If they appear in that order, you can say

drop _9t_9a -- _7t_fb; /* note the double dashes */

or you could simply mention the variables that you want to keep in a keep statement. The others will be dropped.

Re: Drop variables without directly mention them or without DROP statement

webart999ARM — Tue, 04 Aug 2020 13:59:54 GMT

I don't say that il will not work. I'm just seeking a shorter solution.

Re: Drop variables without directly mention them or without DROP statement

PaigeMiller — Tue, 04 Aug 2020 14:09:44 GMT

@webart999ARM wrote:

I don't say that il will not work. I'm just seeking a shorter solution.

Shorter? How about the solution from @PGStats above?

If that's not it, explain the criteria you would want to use to determine what variables to drop.

Re: Drop variables without directly mention them or without DROP statement

webart999ARM — Tue, 04 Aug 2020 14:20:03 GMT

"drop _9t_9a -- _7t_fb;" it's an obviously shorter solution, but '--' can cause unexpected results after data update, I think you know what I'm talking about.
The solution for that could be to define variables in that exact order before the drop, but in that case, again we will have 36 variables mentioned in 'length' or 'retain' statement.
I will use 'keep' for now.

Re: Drop variables without directly mention them or without DROP statement

Reeza — Tue, 04 Aug 2020 14:49:38 GMT

Here is a reference that illustrates how to refer to variables and datasets in a short cut list:
https://blogs.sas.com/content/iml/2018/05/29/6-easy-ways-to-specify-a-list-of-variables-in-sas.html

You can short cut your references if you have a naming convention. The article above illustrates the methods to shorten a list of variables and make them more dynamic. You can drop all variables that start with _9T with the following line for example.

drop _9T: ;

@webart999ARM wrote:

"drop _9t_9a -- _7t_fb;" it's an obviously shorter solution, but '--' can cause unexpected results after data update, I think you know what I'm talking about.
The solution for that could be to define variables in that exact order before the drop, but in that case, again we will have 36 variables mentioned in 'length' or 'retain' statement.
I will use 'keep' for now.

Re: Drop variables without directly mention them or without DROP statement

s_lassen — Tue, 04 Aug 2020 15:08:28 GMT

There are several ways of mentioning multiple variables in a DROP statement (or elsewhere):

drop _9T_AA--7T_FB - drops the variables if they are in that order on the data step data vector
drop _: - drops all variables beginning with an underscore. I very often define temporary variables with an underscore first, and then use exactly that statement to drop them
drop _9T_: _8T_: _3T_: _7T_: - a variation on the above, a bit more refined, should get all the variables mentioned

If none of these work for you, you may have to do some more advanced stuff. One is using a macro to define the exact names:

%macro droplist(prefixes,suffixes);
  %local i1 i2 w1;
  %do i1=1 %to %sysfunc(countw(&prefixes));
      %let w1=%scan(&prefixes,&i1);
      %do i2=1 %to %sysfunc(countw(&suffixes)); _&w1._%scan(&suffixes,&i2)%end;
      %end;
%mend;

data want;
  set have;
  drop %droplist(9T 8T 3T 7T,AA AB BA BB DA EB FB) _dummy xx p3;
run;

I put in the extra variables in the DROP example, just to show how the macro can be used very flexibly.

Re: Drop variables without directly mention them or without DROP statement

whymath — Tue, 04 Aug 2020 15:19:51 GMT

Sounds like you want an easy text pattern generator.

data _null_;
	length text $1024.;
	do i = 9,8,7,3;
		do j = 'AA','AB','BA','BB','CA','CB','DA','EB','FB';
			text = catx(' ',text,cats('_',i,'T_',j));
		end;
	end;
	call symputx('text',text);
run;

%put &=text;

Sure you can transform it to macro.

Re: Drop variables without directly mention them or without DROP statement

webart999ARM — Tue, 04 Aug 2020 16:58:59 GMT

Thank you all guys for your suggested methods.
I find some new techniques for me.

Special thanks to @s_lassen for an advanced solution. I will try to understand the code you have sent 🙂

#bestcommunity