[R] help with loop

Nutter, Benjamin NutterB at ccf.org
Thu Mar 12 14:16:37 CET 2009

Why use a loop? Try using diff()

x <- c(4, 19, 21, 45, 50, 73, 78, 83, 87, 94)

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Rafael Moral
Sent: Thursday, March 12, 2009 9:04 AM
To: r-help at r-project.org
Subject: [R] help with loop

Dear useRs,
I'm trying to write a loop to sum my data in the following way:
(the second - the first) + (the third - the second) + (the fourth - the third) + ...
for each column.

So, I wrote something like this:

  c <- list()
  for(i in 1:ncol(mydata)) {
  for(j in 2:nrow(mydata)) {
  c[[i]] <- sum(yc[j,i] - yc[(j-1),i])

As for the columns it works pretty fine, but it only returns the last subtraction, however, I need the sum of all subtractions.

Any ideas?


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