[R] Equivalents of Matlab's 'find' and 'end'
andy_liaw at merck.com
Thu Oct 7 16:46:37 CEST 2004
There's also the `cheat sheet'
http://cran.r-project.org/doc/contrib/R-and-octave-2.txt that might be
useful for Matlab speakers.
> From: Dimitris Rizopoulos
> Hi Bryan,
> 1. which(x==1)
> 2. X[2:nrow(X),] or X[,2:ncol(X)]
> The "An Introduction to R" document is very usdeful for this kind of
> I hope it helps.
> Dimitris Rizopoulos
> Ph.D. Student
> Biostatistical Centre
> School of Public Health
> Catholic University of Leuven
> Address: Kapucijnenvoer 35, Leuven, Belgium
> Tel: +32/16/396887
> Fax: +32/16/337015
> Web: http://www.med.kuleuven.ac.be/biostat/
> ----- Original Message -----
> From: "Bryan L. Brown" <stonefly at mail.utexas.edu>
> To: <R-help at stat.math.ethz.ch>
> Sent: Thursday, October 07, 2004 4:10 PM
> Subject: [R] Equivalents of Matlab's 'find' and 'end'
> > 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)'
> > 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.
> > If anyone has advice, I'd be grateful,
> > Bryan L. Brown
> > Integrative Biology
> > University of Texas at Austin
> > Austin, TX 78712
> > 512-965-0678
> > stonefly at mail.utexas.edu
> > [[alternative HTML version deleted]]
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