On Fri, May 06, 2011 at 02:28:57PM +1000, andre bedon wrote: > > Hi, > I'm hoping someone can offer some advice:I have a matrix "x" of dimensions > 160 by 10000. I need to create a matrix "y", where the first 7 elements are > equal to x[1]^1/7, then the next 6 equal to x[2]^1/6, next seven x[3]^1/7 and > so on all the way to the 10400000th element. I have implemented this with a > for loop an hour ago and it is still loading, can anyone offer any > suggestions as to how I can create this matrix without using loops? I would > really appreciate any suggestions.
Hi. Since indexing x[1], x[2], ... is used and also the description of y corresponds more to a vector, let me first suggest a solution for vectors. x <- rep(42, times=4) # any vector of even length x <- x/c(7, 6) rep(x, times=rep(c(7, 6), length=length(x))) [1] 6 6 6 6 6 6 6 7 7 7 7 7 7 6 6 6 6 6 6 6 7 7 7 7 7 7 The input vector may be obtained using c() from a matrix. The output vector may be reformatted using matrix(). However, for a matrix solution, a more precise description of the question is needed. Hope this helps. Petr Savicky. ______________________________________________ R-help@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.
