Uwe Ligges wrote: > Werner Wernersen wrote: > >> Hi everybody! >> >> I am sorry to bother you with a question so simple but >> I think there might be a better solution: >> I have a matrix of size 360x501 where I want to check >> the value of each 5th column of each row and replace it (and the 6th, >> 7th, >> 8th column) by zero if the value is less than 1000. I have written a >> double loop >> to do that but that requires a lot of time. >> >> Is there a faster way to achieve this? > > > > Two ways to interpret your question: > > 1) if col5 < 100 replace col5 & col6 & col7 & col8 by 0: > > X[X[,5] < 1000, 5:8] <- 0 > > > 2) if col5 < 100 replace col5 by 0, if col6 < 100 replace col6 by 0, ...: > > > for(i in 5:8) > X[X[,i] < 1000, i] <- 0 > > Uwe Ligges > > > > > >> Thanks, >> Werner >> >> ______________________________________________ >> R-help@stat.math.ethz.ch mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide! >> http://www.R-project.org/posting-guide.html > > > > Thanks for all your answers! Now I did it with for (j in seq(3,length(d[1,]),by=5)) { d[d[,j]<1000,j:(j+3)] <- c(0,0,0,0) } which is so much faster than the double loop.
Thanks again, Werner ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html