R help - Oct 2009 - row subtraction

I don't know if there is a way to do this in R but I want to subtract 
within the same column from different rows.  I want to subtract 
c(r)-c(r-1) and continue down the column until they are all calculated 
and form another column. Again I don't know if R can do this but I 
thought I would ask.

Thanks either way

If I understand what you're asking this is one (although probably not
the easiest or best) way:

X <- as.data.frame(matrix(runif(50), nrow=10))

X.tmp <- rbind(rep(NA, dim(X)[2]), X[1:(dim(X)[1]-1),])

X.new <- X - X.tmp

-Ista

On Sun, Oct 25, 2009 at 5:45 PM, Marsha Melnyk <mmelnyk at stevens.edu>
wrote:
> I don't know if there is a way to do this in R but I want to subtract
> within the same column from different rows. ?I want to subtract
> c(r)-c(r-1) and continue down the column until they are all calculated
> and form another column. Again I don't know if R can do this but I
> thought I would ask.
>
> Thanks either way
>
> ______________________________________________
> R-help at 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.
>


-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org

Marsha Melnyk wrote:
> 
> I don't know if there is a way to do this in R but I want to subtract 
> within the same column from different rows.  I want to subtract 
> c(r)-c(r-1) and continue down the column until they are all calculated 
> and form another column. Again I don't know if R can do this but I 
> thought I would ask.
> 
> 
Can't tell quite what you want -- can you give an example?

Does apply(X,2,diff) do it?

-- 
View this message in context:
http://www.nabble.com/row-subtraction-tp26052146p26053157.html
Sent from the R help mailing list archive at Nabble.com.