What do I put in my CSV file if I do not have an observation for one of my samples?

[caroline_rg]

Hi, 

I have CSV files for all my data. For one of them, I am missing some data from one experimental unit (the sample was damaged, not all the work was able to be completed on it). 

What should I put so SAS will know to not include that sample in the analysis? It's not 0, it just doesn't exist. 

Thank you!

Caroline 

[Patrick]

SAS function FILEEXIST() allows to verify for the existence of an external file by its physical name.

Here some sample code:

%let myfile=C:\temp\test folder\testfile1.txt;
%if %sysfunc(fileexist(&myfile)) %then 
  %do;
    data _null_;
      put "file exists: &myfile";
    run;
  %end;
%else
  %do;
    data _null_;
      put "file does not exist: &myfile";
    run;
  %end;

We would need to see your actual code to give you more targeted advice for you specific code.