This might work for you: returnsFromInception <- sapply(1:NROW(historicalReturns), function(x){ cumsum(historicalReturns[startOffset[1, x] : n, x]) })
On 3/16/07, Murali Menon <[EMAIL PROTECTED]> wrote: > > Folks, > > I have a matrix of historicalReturns, where entry (i, j) is the daily > return > corresponding to date i and equity j. I also have a matrix startOffset, > where entry (1, k) is the row offset in historicalReturns where I entered > into equity k. > > So we have that NCOL(startOffset) = NCOL(historicalReturns). > > Now I would like compute for each column in historicalReturns, the > cumulative return 'returnsFromInception' for the equity starting from the > startOffset date. > > Is there a better way than as follows: > > > n <- NROW(historicalReturns) > returnsFromInception <- matrix(nrow = 1, ncol = > NCOL(historicalInceptionDates)) > > for (i in 1 : NCOL(historicalReturns)) > { > cumReturn <- cumsum(historicalReturns[startOffset[1, i] : n, i]) > returnsFromInception[1, i] <- cumReturn[length(cumReturn)] > } > > This works for me, but seems rather inelegant, and I don't like having to > use a matrix for returnsFromInception and startOffset, where vectors would > work. > > Thanks for your help. > > Murali > > _________________________________________________________________ > It's tax season, make sure to follow these few simple tips > > > ______________________________________________ > R-help@stat.math.ethz.ch 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. > > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? [[alternative HTML version deleted]] ______________________________________________ R-help@stat.math.ethz.ch 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.