specifying data informat using do loops in sas - sas

Question

I have a large data file with data in the following format: country, datatype, year1month1 to year2018month7.
Reading the data using proc import did not work for all data fields. I ended up modifying the SAS datastep code to ensure data format was correct.
However, I am having trouble simplifying the code, namely I would like a do loop to go through all the years and month. This way, I could use current date to figure out the range of dates for the file and the code to create Year/Month variable does not have to repeat 100 times in the file.
data test;
infile 'abc.csv' delimiter = ',' MISSOVER DSD lrecl=32767 firstobs=2 ;
informat Country_Name $34. ;
do i = 1940 to 2018;
do j = 1 to 12;
informat _(i)M(j) best32.;
end;
end;
informat Base_Year $1. ;
format Country_Name $34. ;
do i = 1940 to 2018;
do j = 1 to 12;
format _(i)M(j) best12.;
end;
end;
format Base_Year $1. ;
input
Country_Name $
do i = 1940 to 2018;
do j = 1 to 12;
_(i)M(j) $;
end;
end;
Base_Year $;
run;

Answer 1

There are a few approaches here that could work. The most directly translatable to your approach is to use the macro language.
You need to translate those two loops to something like this:
%do i = 1940 %to 2018;
%do j = 1 %to 12;
informat _&i.M&j. best32.;
%end;
%end;
Notice the % there. This also has to be in a macro; you can't do this in normal datastep code.
I would rewrite it to use a macro like so:
%macro make_ym(startyear=, endyear=, separator=);
%local i j;
%do i = &startyear. %to &endyear.;
%do j = 1 %to 12;
_&i.&separator.&j.
%end;
%end;
%mend make_ym;
data test;
infile 'abc.csv' delimiter = ',' MISSOVER DSD lrecl=32767 firstobs=2 ;
informat Country_Name $34. ;
informat %make_ym(startyear=1940,endyear=2018,separator=M) best32.;
informat Base_Year $1. ;
format %make_ym(startyear=1940,endyear=2018,separator=M) best12.;
format Base_Year $1. ;
input
Country_Name $
%make_ym(startyear=1940,endyear=2018,separator=M)
Base_Year $;
run;
I took out the $ after the yMm bits in the input since you declared them as numeric.

Answer 2

Don't model your data step after the code generated by PROC IMPORT. It does a lot of useless things, like attaching formats and informats to variables that don't need them.
For your problem you just need a simple program like this:
data test;
infile 'abc.csv' dsd dlm= ',' truncover firstobs=2 ;
input Country_Name :$34. Y1940M01 .... Y2018M08 Base_Year :$1. ;
run;
Now the only tricky part is building that list of numerical variables. If the list is small enough you could just put it into a macro variable. Fortunately that is not a problem in this case since using 8 character names (YyyyyMmm) there is room for over 300 years worth in a data step character variable. A variable of length 10,800 bytes should have room for 100 years of month names.
So just run this data step first.
data _null_;
length names $10800 ;
basedate = mdy(1,1,1940);
lastdate = today();
do i=0 to intck('month',basedate,lastdate);
date=intnx('month',basedate,i);
names=catx(' ',names,cats('Y',year(date),'M',put(month(date),Z2.)));
end;
call symputx('names',names);
run;
Now you can use the macro variable in your INPUT statement.
data test;
infile 'abc.csv' dsd dlm= ',' truncover firstobs=2 ;
input Country_Name :$34. &names Base_Year :$1. ;
run;