How to select a record based on the contents of a prior record

[GAO]

I have what I hope is an easy question. I am new to SAS, but I have an extensive IT background.

I have a data file that I want to process in SAS. The general problem is that I only want to process a record if the prior record in the file has a particular value (i,e,. the amt field in the prior record must be negative).

I understand how to subset data based on values in the current record, but since SAS processes record-by-record or observation-by-observation, how do I select a record for processing based on the value of a prior record?

Any thoughts or suggestions would be appreciated.

Thanks,

Gary

 

[MatthiasB]

Hi Gary,

the processing very much depends on your file format (I assume you want to read in flat ASCII). To get you started a little framework:

filename somefile "c:\temp\testme.txt";
data test (drop=dropIt flag);
   length dropIt  $10
          id      $10
		  details $10
		  flag    $1
          ;
   infile someFile missover DLM=" ";
   input id flag;
   if flag eq 'Y'
      then input dropit;
	  else input details;
run;

The file read in contains this:

MIS N
Management
STRAT N
Strategy
CONTRACTS Y
notRead
FIN Y
notRead
IT N
WORKS!

Result is that the lines 'notRead' are not read because of the 'Y' flag in the previous line. I am pretty sure there is a nicer way, but it's a start.

For some reading search for "Formatted Input" in the SAS Help (have this from 8.2).

Cheers,
Matthias

 

[MatthiasB]

Hi again,

in case you want to work with existing tables (but 'previous record' depends on sort order...!), you should have a look at the 'retain' statement in SAS Base. If you get stuck, let me know a few more details on your data structure and requirements.

Cheers,
Matthias