I'm trying to understand the behavior of seq_along in the following example: x <- 1:5; sum(x) y <- 6:10; sum(y) data <- c(x,y) S <- sum( data[seq_along(x)] ) S T <- sum( data[seq_along(y)] ) T Why is T != sum(y) ?
Because, data[seq_along(x)] == data[seq_along(y)], You need this: sum(data[length(x) + seq_along(y)]) On Thu, Feb 25, 2010 at 11:02 AM, Dale Steele <dale.w.steele at gmail.com> wrote:> I'm trying to understand the behavior of seq_along in the following example: > > x <- 1:5; sum(x) > y <- 6:10; sum(y) > > data <- c(x,y) > S <- sum( data[seq_along(x)] ) > S > T <- sum( data[seq_along(y)] ) > T > > Why is T != sum(y) ? > > ______________________________________________ > 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. >-- Henrique Dallazuanna Curitiba-Paran?-Brasil 25? 25' 40" S 49? 16' 22" O
Dale Steele wrote:> > > x <- 1:5; sum(x) > y <- 6:10; sum(y) > > data <- c(x,y) > S <- sum( data[seq_along(x)] ) > S > T <- sum( data[seq_along(y)] ) > T > >If in doubt, divide and conquer: seq_along(x) [1] 1 2 3 4 5> seq_along(y)[1] 1 2 3 4 5 You expected that the second vector is 6,7... Dieter -- View this message in context: http://n4.nabble.com/behavior-of-seq-along-tp1569033p1569049.html Sent from the R help mailing list archive at Nabble.com.
On Feb 25, 2010, at 9:02 AM, Dale Steele wrote:> I'm trying to understand the behavior of seq_along in the following > example: > > x <- 1:5; sum(x) > y <- 6:10; sum(y) > > data <- c(x,y) > S <- sum( data[seq_along(x)] ) > S > T <- sum( data[seq_along(y)] ) > T > > Why is T != sum(y) ?Look at seq_along(y) seq_along returns indices for the purpose of accession of elements, so it starts with 1 and ends with the length of the object. Had you asked for sum(data[y[seq_along(y)]]) you might have achieved your expectation.> > ______________________________________________ > 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.David Winsemius, MD Heritage Laboratories West Hartford, CT