This will give a list, one element per row of oz.gmt, which contains the differently sized vectors as components:
idx <- seq(along = start.hr) f <- function(i) oz.gmt[i, start.hr[i]:24] lapply(idx, f) On 12/5/05, Jaramillo, Renee <[EMAIL PROTECTED]> wrote: > I hope my problem is not too basic to post here. I am a beginner having > problems with some matrix manipulation. The data I am working with are > sites with hourly ozone readings and is in a matrix where each row is a site > and each column is an hourly reading. So for 10 sites, one day's worth of > data is a 10x24 matrix - column 1 is the ozone measurement for midnight GMT, > column 2 is ozone at 1:00am GMT, etc. > > > > My challenge is that I want to create a new matrix with the same sites, BUT > I want the first column to be the hourly ozone reading at midnight LOCAL > time. If all the sites were in the same time zone this would be easy - for > the US Eastern time zone I could do something like: > > oz.est[, 1:19] <- oz.gmt[, 6:24] > > > > The problem is the sites are in different time zones, and I have a separate > vector that indicates which site belongs to which time zone. So sites in > the Eastern time zone I want to extract columns 6-24 from the GMT matrix, > sites in the Central time zone I want to extract columns 7-24 from the GMT > matrix, etc. > > > > Is there a clever way to use matrix indices on my GMT matrix to extract the > columns I need for the sites in the different time zones? I have been > trying different things like this: > > > > # VECTOR WITH HOUR TIME DIFFERENCE BETWEEN SITE AND GMT > > start.hr <- c(6,7,6,8,7,5,7,6,5,6) > > > > # THIS DOESN'T WORK > > oz.local[ , 1: (24-start.hr) ] <- oz.gmt [, (start.hr+1) : 24 ] > > > > # THIS DOESN'T WORK EITHER > > oz.local[ , rep(1,nrow(oz.gmt)) : (24-start.hr) ] <- oz.gmt [, > (start.hr+1) : rep(24,nrow(oz.gmt)) ] > > > > Ultimately I will be working with over 10,000 sites and hourly data over 3 > months so my data matrix will be something like 10,220 x 2208 > > > > > > I'd appreciate any suggestions. Thanks! > > Renee Jaramillo > > > > > > > > > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
