You only need one "for loop" for(i in 2:nrow(myMatrix)) { myMatrix[i-1,i-1] = -1 myMatrix[i-1,i] = 1 }
HTH, Eric On Wed, Aug 8, 2018 at 12:40 PM, Maija Sirkjärvi <maija.sirkja...@gmail.com> wrote: > Thanks! > > If I do it like this: > > myMatrix <- matrix(0,5,5*2-3) > print(myMatrix) > for(i in 2:nrow(myMatrix)) > for(j in 2:ncol(myMatrix)) > myMatrix[i-1,j-1] = -1 > myMatrix[i-1,j] = 1 > print(myMatrix) > > I get the following result: > > [,1] [,2] [,3] [,4] [,5] [,6] [,7] > [1,] -1 -1 -1 -1 -1 -1 0 > [2,] -1 -1 -1 -1 -1 -1 0 > [3,] -1 -1 -1 -1 -1 -1 0 > [4,] -1 -1 -1 -1 -1 -1 1 > [5,] 0 0 0 0 0 0 0 > > However. The result that I would need to get would be like this: > > [,1] [,2] [,3] [,4] [,5] [,6] [,7] > [1,] -1 1 0 0 0 0 0 > [2,] 0 -1 1 0 0 0 0 > [3,] 0 0 -1 1 0 0 0 > [4,] 0 0 0 -1 1 0 0 > [5,] 0 0 0 0 -1 1 0 > > I'd rather not create symmetric matrices as I would really like to learn > how to do this thing "the hard way" as I find matrix iteration to be quite > a basic procedure in everything I'm trying to do. > > Thanks again! > Maija > > > > > ti 7. elok. 2018 klo 17.37 Rui Barradas (ruipbarra...@sapo.pt) kirjoitti: > > > Hello, > > > > If it is not running as you want it, you should say what went wrong. > > Post the code that you have tried and the expected output, please. > > (In fact, the lack of expected output was the reason why my suggestion > > was completely off target.) > > > > Rui Barradas > > > > On 07/08/2018 09:20, Maija Sirkjärvi wrote: > > > Thanks, but I didn't quite get it. And I don't get it running as it > > should. > > > > > > ti 7. elok. 2018 klo 10.47 Martin Maechler (maech...@stat.math.ethz.ch > > > <mailto:maech...@stat.math.ethz.ch>) kirjoitti: > > > > > > > > > > Thanks for help! > > > > However, changing the index from i to j for the column vector > > > changes the > > > > output. I would like the matrix to be the following: > > > > > > > -1 1 0 0 0 0 0 > > > > 0 -1 1 0 0 0 0 > > > > 0 0 -1 1 0 0 0 > > > > ..... > > > > etc. > > > > > > > How to code it? > > > > > > as Enrico Schumann showed you: Without any loop, a very nice > > > R-ish way (see his message)! > > > > > > Martin > > > > > > > Best, > > > > Maija > > > > > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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. > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.