... "(R is case sensitive, so "C" has no such problem)."
Well, not quite. Try ?C To add to the previous comments, Dr. Gordon appears to need to do her/his homework and spend some time with an R tutorial or two before posting further here. There are many good ones on the web. Some recommendations can be found here: https://www.rstudio.com/online-learning/#R Cheers, Bert Bert Gunter "The trouble with having an open mind is that people keep coming along and sticking things into it." -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) On Wed, Apr 27, 2016 at 12:57 PM, Jeff Newmiller <[email protected]> wrote: > "c" an extremely commonly-used function. Functions are first-class objects > that occupy the same namespaces that variables do, so they can obscure each > other. In short, don't use variables called "c" (R is case sensitive, so "C" > has no such problem). > > Wherever possible, avoid incremental concatenation like the plague. If you > feel you must use it, at least concatenate in lists and then use functions > like unlist, do.call, or pre-allocate vectors or matrix-like objects with > unuseful values like NA and then overwrite each element in the vector or > matrix-type object in a loop like your first one. > -- > Sent from my phone. Please excuse my brevity. > > On April 27, 2016 3:25:14 PM GMT+01:00, "Gordon, Fabiana" > <[email protected]> wrote: >>Hello, >> >>Suppose the you need a loop to create a new variable , i.e., you are >>not reading data from outside the loop. This is a simple example in >>Matlab code, >> >>for i=1:5 >>r1=randn >>r2=randn >>r=[r1 r2] >>c(i,:)=r; % creation of each row of c , % the ":" symbol indicates >>all columns. In R this would be [i,] >>end >> >>The output of interest is c which I'm creating inside the "for" loop >>-also the index used in the loop is used to create c. In R I had to >>create c as an empty vector (numeric() ) outside the loop, otherwise I >>get an error message saying that c doesn't exit. >> >>The other issue is the concatenation. In each iteration I'm creating >>the rows of c by placing the new row (r) below the previous one so >>that c becomes a 5 x 2 matrix. >>In R, it seems that I have no choice but use the function "rbind". I >>managed to write this code in R . However, I'm not sure that if instead >>of creating a new variable using the index in the "for" loop , I >>wanted to use the index to read data, e.g. suppose I have a 2 X 10 >>matrix X and suppose I want to calculate the sin () for each 2 x 2 >>sub-matrix of and stored in a matrix A. Then the code would be >>something like this, >> >>for i=1:5 >>A(:, 2*i-1:2*i)= sin(X(:, 2*i-1:2*i)) % the ":" symbol indicates all >>rows >>end >> >>Many Thanks, >> >>Fabiana >> >> >>Dr Fabiana Gordon >> >>Senior Statistical Consultant >>Statistical Advisory Service, School Of Public Health, >>Imperial College London >>1st Floor, Stadium House, 68 Wood Lane, >>London W12 7RH. >> >>Tel: 020 7594 1749 >>Email: >>[email protected]<mailto:[email protected]> >>Web: >>www.imperial.ac.uk/research-and-innovation/support-for-staff/stats-advice-service/<http://www.imperial.ac.uk/research-and-innovation/support-for-staff/stats-advice-service/> >> >> >> >> [[alternative HTML version deleted]] >> >>______________________________________________ >>[email protected] 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]] > > ______________________________________________ > [email protected] 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. ______________________________________________ [email protected] 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.
