SAS: Dynamically determine input fields from a dataset - sas

Question

I am trying to parse a delimited dataset with over 300 fields. Instead of listing all the input fields like
data test;
infile "delimited_filename.txt"
DSD delimiter="|" lrecl=32767 STOPOVER;
input field_A:$200.
field_B :$200.
field_C:$200.
/*continues on */
;
I am thinking I can dump all the field names into a file, read in as a sas dataset, and populate the input fields - this also gives me the dynamic control if any of the field names changes (add/remove) in the dataset. What would be some good ways to accomplish this?
Thank you very much - I just started sas, still trying to wrap my head around it.

Answer 1

This worked for me - Basically "write" data open code using macro language and run it.
Note: my indata_header_file contains 5 columns: Variable_Name, Variable_Length, Variable_Type, Variable_Label, and Notes.
%macro ReadDsFromFile(filename_to_process, indata_header_file, out_dsname);
%local filename_to_process indata_header_file out_dsname;
/* This macro var contain code to read data file*/
%local read_code input_in_line;
%put *** Processing file: &filename_to_process ...;
/* Read in the header file */
proc import OUT = ds_header
DATAFILE = &indata_header_file.
DBMS = EXCEL REPLACE; /* REPLACE flag */
SHEET = "Names";
GETNAMES = YES;
MIXED = NO;
SCANTEXT = YES;
run;
%let id = %sysfunc(open(ds_header));
%let NOBS = %sysfunc(attrn(&id.,NOBS));
%syscall set(id);
/*
Generates:
data &out_dsname.;
infile "&filename_to_process."
DSD delimiter="|" lrecl=32767 STOPOVER FIRSTOBS=3;
input
'7C'x
*/
%let read_code = data &out_dsname. %str(;)
infile &filename_to_process.
DSD delimiter=%str("|") lrecl=32767 STOPOVER %str(;)
input ;
/*
Generates:
<field_name> : $<field_length>;
*/
%do i = 1 %to &NObs;
%let rc = %sysfunc(fetchobs(&id., &i));
%let VAR_NAME = %sysfunc(getvarc(&id., %sysfunc(varnum(&id., Variable_Name)) ));
%let VAR_LENGTH = %sysfunc(getvarn(&id., %sysfunc(varnum(&id., Variable_Length)) ));
%let VAR_TYPE = %sysfunc(getvarc(&id., %sysfunc(varnum(&id., Variable_Type)) ));
%let VAR_LABEL = %sysfunc(getvarc(&id., %sysfunc(varnum(&id., Variable_Label)) ));
%let VAR_NOTES = %sysfunc(getvarc(&id., %sysfunc(varnum(&id., Notes)) ));
%if %upcase(%trim(&VAR_TYPE.)) eq CHAR %then
%let input_in_line = &VAR_NAME :$&VAR_LENGTH..;
%else
%let input_in_line = &VAR_NAME :&VAR_LENGTH.;
/* append in_line statment to main macro var*/
%let read_code = &read_code. &input_in_line. ;
%end;
/* Close the fid */
%let rc = %sysfunc(close(&id));
%let read_code = &read_code. %str(;) run %str(;) ;
/* Run the generated code*/
&read_code.
%mend ReadDsFromFile;

Answer 2

Sounds like you want to generate code based on metadata. A data step is actually a lot easier to code and debug than a macro.
Let's assume you have metadata that describes the input data. For example let's use the metadata about the SASHELP.CARS. We can build our metadata from the existing DICTIONARY.COLUMNS metadata on the existing dataset. Let's set the INFORMAT to the FORMAT since that table does not have INFORMAT value assigned.
proc sql noprint ;
create table varlist as
select memname,varnum,name,type,length,format,format as informat,label
from dictionary.columns
where libname='SASHELP' and memname='CARS'
;
quit;
Now let's make a sample text file with the data in it.
filename mydata temp;
data _null_;
set sashelp.cars ;
file mydata dsd ;
put (_all_) (:);
run;
Now we just need to use the metadata to write a program that could read that data. All we really need to do is define the variables and then add a simple INPUT firstvar -- lastvar statement to read the data.
filename code temp;
data _null_;
set varlist end=eof ;
by varnum ;
file code ;
if _n_=1 then do ;
firstvar=name ;
retain firstvar ;
put 'data ' memname ';'
/ ' infile mydata dsd truncover lrecl=1000000;'
;
end;
put ' attrib ' name 'length=' #;
if type = 'char' then put '$'# ;
put length ;
if informat ne ' ' then put #10 informat= ;
if format ne ' ' then put #10 format= ;
if label ne ' ' then put #10 label= :$quote. ;
put ' ;' ;
if eof then do ;
put ' input ' firstvar '-- ' name ';' ;
put 'run;' ;
end;
run;
Now we can just run the generated code using %INCLUDE.
%include code / source2 ;