On Thursday 07 October 2004 09:10, Bryan L. Brown wrote: > Sorry if these questions have been asked recently--I'm new to this > list. > > I'm primarily a Matlab user who is attempting to learn R and I'm > searching for possible equivalents of commands that I found very > handy in Matlab. So that I don't seem ungrateful to those who may > answer, I HAVE determined ways to carry out these processes in 'brute > force' sorts of ways in R code, but they lack the elegance and > simplicity of the Matlab commands. Also, if you know that no such > commands exist, that bit of knowledge would be helpful to know so > that I don't continue fruitless searches. > > The first is Matlab's 'find' command. > This is one of the most useful commands in Matab. Basically, if X is > the vector > > X=[3, 2, 1, 1, 2, 3] > > the command > > 'find(X==1)'
which(X==1) > would return the vector [3, 4] which would indicate that the vector X > had the value of 1 at the 3 and 4 positions. This was an extremely > useful command for subsetting in Matlab. The closest thing I've > found in R has been 'match' but match only returns the first value as > opposed to the position of all matching values. > > The second Matlab command that I'd like to find an R equivalent for > is 'end'. 'end' is just a simple little command that indicates the > end of a row/column. It is incredibly handy when used to subset > matrices like > > Y = X(2:end) > > and produces Y=[2, 1, 1, 2, 3] if the X is the same as in the > previous example. This cutsie little command was extremely useful > for composing programs that were flexible and could use input > matrices of any size without modifying the code. I realize that you > can accomplish the same by Y <- X[2:length(X)] in R, but this method > is ungainly, particularly when subsetting matrices rather than > vectors. I don't know of anything better than length(X) or nrow/ncol(X), but you could do X[-1], which is at least as elegant for your example, and would work for matrices as well. Hth, Deepayan ______________________________________________ [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
