Hey, Thanks for your great inputs. While "index = apply(mat == 0, MARGIN = 1, any)" gives you an idea of the rows containing zero(s), "index<-data[!apply(data==0,MARGIN=1,any),]" does the actual job of removing the rows with zeros. Kind regards Ogbos
On 9 March 2010 15:12, Paul Hiemstra <p.hiems...@geo.uu.nl> wrote: > Dimitris Rizopoulos wrote: > >> >> >> On 3/9/2010 1:36 PM, Paul Hiemstra wrote: >> >>> Dimitris Rizopoulos wrote: >>> >>>> one approach is the following: >>>> >>>> mat <- matrix(rnorm(100*45), 100, 45) >>>> mat[sample(100*45, 50)] <- 0 >>>> >>>> index <- rowMeans(mat == 0) == 0 >>>> mat[index, ] >>>> >>> Dimitris, >>> >>> You use quite a complicated syntax to get the index. I think the >>> following syntax using apply is more easy to understand: >>> >> >> well, this way is much more efficient to compute, especially if you have >> many rows. Compare the following to see the difference: >> >> mat <- matrix(rnorm(2*1e06), 1e06, 2) >> mat[sample(2*1e06, 50)] <- 0 >> >> system.time(index1 <- !apply(mat == 0, MARGIN = 1, any)) >> >> system.time(index2 <- rowMeans(mat == 0) == 0 ) >> >> all.equal(index1, index2) >> > Point taken, I totally agree that for large matrices you should use your > approach. Didn't know that it made such a difference, great to learn > something new :). But I still like the other syntax more ;). > > cheers, > Paul > > >> >> Best, >> Dimitris >> >> >> # Note, MARGIN equal to 1 means loop over rows >>> # If any member of a row is zero >>> index = apply(mat == 0, MARGIN = 1, any) >>> # If all members of a row are zero >>> index = apply(mat == 0, MARGIN = 1, all) >>> >>> cheers and hope it helps, >>> Paul >>> >>>> >>>> >>>> I hope it helps. >>>> >>>> Best, >>>> Dimitris >>>> >>>> >>>> On 3/9/2010 11:05 AM, ogbos okike wrote: >>>> >>>>> Hi Everybody, >>>>> I have a matrix of about 45 columns. Some of the rows contain zeros. >>>>> Using >>>>> >>>>>> data1<-data[complete.cases(data),], I can remove the "NA" rows. But >>>>>> I am >>>>>> >>>>> unable to tackle that of zeros. >>>>> Can anybody give me an idea of how to remove rows containing zeros in a >>>>> matrix. >>>>> Thanks so much >>>>> Best >>>>> Ogbos >>>>> >>>>> [[alternative HTML version deleted]] >>>>> >>>>> ______________________________________________ >>>>> R-help@r-project.org mailing list >>>>> 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. >>>>> >>>>> >>>> >>> >>> >> > > -- > Drs. Paul Hiemstra > Department of Physical Geography > Faculty of Geosciences > University of Utrecht > Heidelberglaan 2 > P.O. Box 80.115 > 3508 TC Utrecht > Phone: +3130 274 3113 Mon-Tue > Phone: +3130 253 5773 Wed-Fri > http://intamap.geo.uu.nl/~paul <http://intamap.geo.uu.nl/%7Epaul> > > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list 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.
