How to subset automatically in SAS? - sas

Question

I am new to SAS, so this might be a silly type of question.
Assume there are several datasets with similar structure but different column names. I want to get new datasets with the same number of rows but only a subset of columns.
In the following example, Data_A and Data_B are original datasets and SubA and SubBare what I want. What is the efficient way of deriving SubA and SubB?
DATA A_auto;
LENGTH A_make $ 20;
INPUT A_make $ 1-17 A_price A_mpg A_rep78 A_hdroom A_trunk A_weight A_length A_turn A_displ A_gratio A_foreign;
CARDS;
AMC Concord 4099 22 3 2.5 11 2930 186 40 121 3.58 0
AMC Pacer 4749 17 3 3.0 11 3350 173 40 258 2.53 0
Audi Fox 6295 23 3 2.5 11 2070 174 36 97 3.70 1
;
RUN;
DATA B_auto;
LENGTH make $ 20;
INPUT B_make $ 1-17 B_price B_mpg B_rep78 B_hdroom B_trunk B_weight B_length B_turn B_displ B_gratio B_foreign;
CARDS;
Toyota Celica 5899 18 5 2.5 14 2410 174 36 134 3.06 1
Toyota Corolla 3748 31 5 3.0 9 2200 165 35 97 3.21 1
VW Scirocco 6850 25 4 2.0 16 1990 156 36 97 3.78 1
;
RUN;
DATA SubA;
set A_auto;
keep A_make A_price;
RUN;
DATA SubB;
set B_auto;
keep B_make B_price;
RUN;

Answer 1

Here's my new answer. This introduces quite a few concepts, but all are necessary to complete this task.
First of all I would store the required part variable names (the suffixes that are common to all datasets) in a new dataset. This keeps them all in one place and makes it easier to change if required.
The next step is to create a regular expression (regex) search string that combines all the names, separated by a pipe (|), which is the regex symbol for or. I've also added a $ symbol to end of the names, this ensures only variables ending with the part names will be selected.
select into :[macroname] is the method to create macro variables within proc sql
Then I set up a macro to extract the specific variable names for the current dataset and use those names to create a view (like my original answer)
The dictionary library referenced in the proc sql is a metadata library that contains information on all active libraries, tables, columns etc, so is a good source of identifying what the actual variable names are called (based on the regex search string created earlier).
You won't need the proc print in your code, I just put it in to show everything is working as expected.
Let me know if this works for you
/* create intial datasets */
DATA A_auto;
LENGTH A_make $ 20;
INPUT A_make $ 1-17 A_price A_mpg A_rep78 A_hdroom A_trunk A_weight A_length A_turn A_displ A_gratio A_foreign;
CARDS;
AMC Concord 4099 22 3 2.5 11 2930 186 40 121 3.58 0
AMC Pacer 4749 17 3 3.0 11 3350 173 40 258 2.53 0
Audi Fox 6295 23 3 2.5 11 2070 174 36 97 3.70 1
;
RUN;
DATA B_auto;
LENGTH B_make $ 20;
INPUT B_make $ 1-17 B_price B_mpg B_rep78 B_hdroom B_trunk B_weight B_length B_turn B_displ B_gratio B_foreign;
CARDS;
Toyota Celica 5899 18 5 2.5 14 2410 174 36 134 3.06 1
Toyota Corolla 3748 31 5 3.0 9 2200 165 35 97 3.21 1
VW Scirocco 6850 25 4 2.0 16 1990 156 36 97 3.78 1
;
RUN;
/* create dataset containing partial name of variables to keep */
data keepvars;
input part_name $ :20.;
datalines;
_make
_price
;
run;
/* create regular expression search string from partial names */
proc sql noprint;
select
cats(part_name,'$') /* '$' matches end of string */
into
:name_str separated by '|' /* '|' is an 'or' search operator in regular expressions */
from
keepvars;
quit;
%put &name_str.; /* print search string to log */
/* macro to create views from datasets */
%macro create_views (dsname, vwname); /* inputs are dataset name being read in and view name being created */
/* extract specific variable names to be kept, based on search string */
proc sql noprint;
select
name
into
:vars separated by ' '
from
dictionary.columns
where
libname = 'WORK'
and memname = upper("&dsname.")
and prxmatch("/&name_str./",strip(name))>0; /* prxmatch is regular expression search function */
quit;
%put &vars.; /* print variables to keep to log */
/* create views */
data &vwname. / view=&vwname.;
set &dsname. (keep=&vars.);
run;
/* test view by printing */
proc print data=&vwname.;;
run;
%mend create_views;
/* run macro for each dataset */
%create_views(A_auto, SubA);
%create_views(B_auto, SubB);