[R] Converting SAS Data code to R.

[David Winsemius]

I am contemplating bringing in and merging three NHANES-III datasets  
from the National Center for Health Statistics that are fixed format  
with record length=3348, line counts around 20,000 and described by  
SAS DATA steps. I have downloaded and linked similar datasets from the  
Continuous NHANES public data releases, but never ones with this many  
variables at once. In the prior effort I managed the task by some cut- 
paste-editing from the SAS code file into a corresponding read.fwf R  
call, but the earlier NHANES-III data is far more voluminous than the  
more recent "Continuous" version. I am wondering if anyone has  
experience with such a process and would be willing to share some  
advice? The SAS code can be seen here:

ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Datasets/NHANES/NHANESIII/1A/adult.sas

The main code file Data step starts out...
     FILENAME ADULT "D:\Questionnaire\DAT\ADULT.DAT" LRECL=3348;
     *** LRECL includes 2 positions for CRLF, assuming use of PC SAS;
     DATA WORK;
       INFILE ADULT MISSOVER;
       LENGTH
         SEQN      7
         DMPFSEQ   5
         DMPSTAT   3
         DMARETHN  3
         DMARACER  3
         DMAETHNR  3
         HSSEX     3
The corresponding positions in the INPUT section are
      INPUT
         SEQN     1-5
         DMPFSEQ  6-10
         DMPSTAT  11
         DMARETHN 12
         DMARACER 13
         DMAETHNR 14
         HSSEX    15
The note about CRLF appears to be implying that those characters are  
being counted as part of the length of the first variable, SEQN, but  
that there are only 5 meaningful positions. I suppose I can find out  
by trial and error how to read such files, but it would save me some  
time if anyone in the audience has worked through this on this data  
before.
One thought would be to import the data with the SAS work-alike  
program, WKS, (which I have not used before) and then to read in with  
read.xport from the foreign library. That would obviate the need to  
understand the character position issue, but probably has a time  
commitment to get it up and running and learn how to use it.
Another thought would be to parse the fixed width SAS Data step code  
into pieces and build a data.frame from which I then extract the  
row.names, col.names, and colClasses from that centralized structure.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT