Hi Nick, Take a look at ?cbind and ?"["
Here is some (untested) code that is how I might go about it. It takes advantage of the fact that a single value will be recycled to equal the necessary length. Then I just assign over the NA in row 24. myframe <- cbind(myframe, New = NA) myframe[24, "New"] <- with(myframe, A[1] - A[24]) New will be an all NA column except for row 24. Cheers, Josh On Thu, Oct 28, 2010 at 11:47 AM, Nick Ackerman <nick.acker...@pgn.com> wrote: > > Hi All, > > I have a data frame (myframe) with variables (columns) A,B,C and 100 records > (rows) for each. Column A is numeric. I would like to append a column to > myframe that subtracts the value in row 24 of A from row 1 of A. In this > procedure the first 23 rows of the new column will necessarily be blank > (NA). Can anyone provide guidance for me here? > > Thanks in advance for your time. > > Nick > -- > View this message in context: > http://r.789695.n4.nabble.com/How-to-perform-arithmetic-across-rows-tp3017905p3017905.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org 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. > -- Joshua Wiley Ph.D. Student, Health Psychology University of California, Los Angeles http://www.joshuawiley.com/ ______________________________________________ R-help@r-project.org 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.
