Hello, Is there an option to include multiple counters in a single for loop in R? For instance, in python there is for i,j in zip(x,range(0,len(x))): Any suggestions? [[alternative HTML version deleted]]
Sort of, but you typically wouldn't need to in R because of vectorization, which buries the iteration in the underlying C code. Here's an example that may clarify what I mean: x <- cbind(1:5,6:10) x ## a 2 column matrix ## get squares of all elements of x ## method 1 m1 <-x^2 ##method 2: square the column vectors m2 <- x for (i in 1:2)m2[,i] <- m2[,i]^2 identical(m1,m2) ## of course, one could do this by row vectors, too ## method 3: loop through each element m3 <- x ix <- as.matrix(expand.grid(1:5,1:2)) ix m3[ix]^2 ## matrix indexing of an array. This produces a vector,though. Note also that there is an "iterators" package in R which implements python-like iterators.I don't know how efficient it is, however. My overall advice would be that you should try to program in R's native paradigms, which emphasize whole object manipulation through vectorization, rather than trying to use Python's, especially if efficiency is a consideration. Feel free to ignore of course. 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 Fri, Aug 24, 2018 at 6:44 AM Deepa <deepamahm.iisc at gmail.com> wrote:> Hello, > > Is there an option to include multiple counters in a single for loop in R? > > For instance, in python there is > > for i,j in zip(x,range(0,len(x))): > > > Any suggestions? > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help at 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]]
I don't know of any such option, but it's easy enough to achieve
something more or less equivalent.
x <- runif(5)
for (ir in seq(nrow(myi <- cbind(x, 1:length(x))))) {
i <- myi[ir,1]
j <- myi[ir,2]
cat(i,j,'\n')
}
I consider that for() statement to be ugly and unreadable. Normally I would
build the matrix myi before constructing the loop, and make other changes for
clarity. But in this instance I wanted to make it a one-liner, just to more or
less mimic the python.
And having now read Bert's reply, he makes a good point. For many things one
might want to do with such a loop, R can do them without an explicit loop.
-Don
--
Don MacQueen
Lawrence Livermore National Laboratory
7000 East Ave., L-627
Livermore, CA 94550
925-423-1062
Lab cell 925-724-7509
?On 8/24/18, 6:44 AM, "R-help on behalf of Deepa" <r-help-bounces
at r-project.org on behalf of deepamahm.iisc at gmail.com> wrote:
Hello,
Is there an option to include multiple counters in a single for loop in R?
For instance, in python there is
for i,j in zip(x,range(0,len(x))):
Any suggestions?
[[alternative HTML version deleted]]
______________________________________________
R-help at 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.
look at the map2 function in the purrr package. On August 24, 2018 6:44:19 AM PDT, Deepa <deepamahm.iisc at gmail.com> wrote:>Hello, > >Is there an option to include multiple counters in a single for loop in >R? > >For instance, in python there is > >for i,j in zip(x,range(0,len(x))): > > >Any suggestions? > > [[alternative HTML version deleted]] > >______________________________________________ >R-help at 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.-- Sent from my phone. Please excuse my brevity.