So, I take it, given that the use of a pipe is suggested for 
sequential reading, that the standard approach to processing a data 
frame is to load the entire file?  Please correct if wrong.

BTW, I am not interested in finding direct translations of SAS data 
step statements to R, but instead in finding an approach by which I 
can address the type of problems I consistent have to deal with 
(grouped processing with retention of baseline records, etc.).  I'll 
read more on the indexing as a means of dealing with relative position issues

Thanks,

Gerard



>You could also load the entire file into a DBMS then pull parts of it
>into R, or read specific lines through a pipe e.g.
>readLines(pipe("sed, grep, python... command")).
>
>Don't try to replicate the SAS processing into R. The exact
>translations of the SAS DATA STEP usage of _N_, first., last., retain
>etc into R would be: inefficient, ugly, retrogressive, wrong, rigid,
>complicated, silly and so on. For a start, read up on indexing - this
>seemingly simple and innocuous R feature is in fact far more powerful
>than the entire DATA STEP with its whole bag of tricks. Then search
>the list for similar questions, for example
>http://thread.gmane.org/gmane.comp.lang.r.general/44332/focus=44343
>
>
>>-----Original Message-----
>>From: r-help-bounces@stat.math.ethz.ch
>>[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Gerard Smits
>>Sent: Sunday, January 21, 2007 2:22 PM
>>To: r-help@stat.math.ethz.ch
>>Subject: [R] sequential processing
>>
>>Like many others, I am new to R but old to SAS.
>>
>>Am I correct in understanding that R processes a data frame in a
>>sequential ly?  This would imply that large input files could be
>>read, without the need to load the entire file into memory.
>>Related to the manner of reading a frame, I have been looking for the
>>equivalent of SAS _n_ (I realize that I can use a variant of which to
>>identify an index value) as well as  useful SAS features such as
>>first., last., retain, etc.  Any help with this conversion
>>appreciated.
>>
>>Thanks,
>>
>>Gerard Smits
>>
>>______________________________________________
>>R-help@stat.math.ethz.ch mailing list
>>https://stat.ethz.ch/mailman/listinfo/r-help
>>PLEASE do read the posting guide
>>http://www.R-project.org/posting-guide.html
>>and provide commented, minimal, self-contained, reproducible code.

	[[alternative HTML version deleted]]

