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: [EMAIL PROTECTED] >>[mailto:[EMAIL PROTECTED] 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]] ______________________________________________ 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.