what is wrong with the following sas code? - sas

Question

I am new to sas. I have written a basic code but it is not working. Can somebody help me figure out what is wrong with the code. I wish to append the datasets.
options mprint mlogic symbolgen;
%macro temp();
%let count = 0;
%if &count = 0 %then %do;
data temp;
set survey_201106;
%let count = %eval(&count +1);
%end;
%else %do;
%do i = 201107 %to 201108;
data temp;
set temp survey_&i;
%end;
%end;
run;
%mend;
%temp;

Answer 1

You are setting &count to 0 at the beginning of the macro, so the %else clause will never be executed.
I'm not sure what your aim is, but it looks like you just want to concatenate 3 datasets and store in a new dataset. If so, will this not suffice:
data temp;
set survey_201106-survey_201108;
run;
This creates a dataset called temp and populates it with the the contents of survey_201106, survey_201107 and survey_201108 in order. The - tells SAS that you want the all the datasets named survey_20110* between survey_201106 and survey_201108 inclusive.
Details of the syntax.

Answer 2

options mprint mlogic symbolgen;
%macro temp();
proc sql noprint;
create table table_list as
select monotonic() as num,memname
from dictionary.tables
where libname = 'WORK' and memname contains 'SURVEY_';
quit;
proc sql noprint;
select count(*) into :cnt
from table_list;
quit;
%do i = 1 %to &cnt.;
%if &i eq 1 and %sysfunc(exist(work.temp)) %then %do;
proc sql;
drop table work.temp;
quit;
%end;
proc sql noprint;
select memname into :memname
from table_list
where num = &i.;
quit;
proc append base = temp data = &memname. force;
run;
%end;
%mend;
%temp;
Working: Above code will append all the work data sets whose names starting with
'SURVEY_' to temp data set.
dictionary.tables is used to create a data set which will contain the list of data sets whose names starts with 'survey_'.
table_list data set:
num memname
1 survey_201106
2. survey_201107
3. survey_201108
cnt macro variable is created to hold number of such data sets
Within loop, each data set present the list of data set names (in table table_list) will be appended to work.temp data set

Answer 3

What you're probably trying to do is create a macro that appends (without using proc append for some reason) when a dataset exists, or creates it new when it does.
SAS is not like r or other similar languages, where you have to control largely everything that happens. SAS's strength is that you can ask it to do common things with only a line or two of code. SAS is what's commonly called a 4th Generation Language for this reason: you're not supposed to control all of the little bits. That's a waste of time. Use the Procedures (PROC...) and constructs SAS provides you.
In this case, PROC APPEND does exactly what this whole macro does. It creates a dataset or appends new rows to it if it already exists.
proc append base=temp data=in_data;
run;
Now, if you're trying to learn the macro language and using this concept as a learning tool only, it is possible to do this in a macro that's not all that different from yours.
Note: This is not a good way to do this. It might be useful for learning macro concepts, but it should not be used as an example of good code. Despite my improvements, it is still not the way you should do this; proc append or SRSwift's example are better.
One thing I'm going to introduce here: a macro parameter. A good rule of macro programming is that all macros should have parameters. If there's no possible parameter, it should usually be possible to do without needing a macro. Parameters are what make macros useful, most of the time. In this case I'm going to rewrite your macro to take one append dataset as a parameter and one 'base' dataset. In your example, temp was the base dataset and survey_1106 etc. are the append datasets.
Also, &count needs to be a global macro variable. In SAS, variables created inside a macro are by default local in scope - ie, they only are defined inside one run of the macro and then disappear. This is nearly identical to functions in c/etc. languages (a bit different from r, which uses lexical scoping, and you might be expecting given how you wrote this). There are some funny rules, though, but for now we'll just go with this. global macro variables, which include any variable that has already been defined in the global scope, are available in all macro iterations (and outside of macros).
So:
%macro append_dataset(base=,append=);
%if &count=0 %then %do;
data &base.;
set &append.;
run;
%end;
%else %do;
data &base.;
set &base. &append.;
run;
%end;
%let count=%eval(&count.+1);
%mend append_dataset;
%let count=0;
%append_dataset(base=temp,append=survey_1106);
%append_dataset(base=temp,append=survey_1107);
%append_dataset(base=temp,append=survey_1108);
Now, you could generate those calls through an external method (such as dictionary.tables as in Harshad's example). You also could add another element to the macro, which is to iterate over all of the elements in a list provided as append. You could also hardcode the list in a %do loop, as you did in the initial example (but I think that's bad practice to get into). You could literally do that in my macro:
%macro append_dataset(base=,append=);
%do survey=201106 to 201108;
%if &count=0 %then %do;
data &base.;
set survey_&survey.;
run;
%end;
%else %do;
data &base.;
set &base. survey_&survey.s;
run;
%end;
%let count=%eval(&count.+1);
%end;
%mend append_dataset;
Notice the count increment is inside the do loop - that's one of the places you went wrong here. Otherwise this is just adding an outer loop and changing the append mentions to the calculated values from the loop. But again, this is fairly poor coding practice - the loop should at minimum be constructed from a macro parameter.