I wasn't thinking straight. > old.data= 11:20 > recalc.please= (old.data%%2==0) > old.data[recalc.please] [1] 12 14 16 18 20 > new.data[recalc.please]= old.data[recalc.please]^2 Error in new.data[recalc.please] = old.data[recalc.please]^2 : object 'new.data' not found
# this is where I had given up, but the following works: > new.data=old.data > new.data[recalc.please]= old.data[recalc.please]^2 > new.data [1] 11 144 13 196 15 256 17 324 19 400 sorry, guys. /iaw ---- Ivo Welch ([email protected]) On Tue, Mar 27, 2012 at 7:27 PM, ilai <[email protected]> wrote: > It is (at least for me) really unclear what the problem is, or how > it's related to mclapply. > You say > " this works fine, except that what I want to get NA's in the return > positions that were not recalculated. then, I can write >> >> newdata$y <- ifelse ( is.na(olddata$y), mc.byselectrows( olddata, >> is.na(olddata$y), fun.calc.y ), olddata$y ) > " > Why ??? > Are you applying the function twice ? than why not simply > v1.1 <- mc.byselectrows( d, loc<1, function(x) x[,2]^2 ) > the second time ? > > If the problem is in keeping track of which rows got calculated, why > not rename with the row.names omitted after mclapply (probably a good > idea anyway): > > FUN.ON.ROWS <- function(.index, ...) > as.matrix(FUN(data.notdone[.index,], ...)) > soln <- mclapply( as.list(1:nrow(data.notdone)) , FUN.ON.ROWS, ... ) > rv <- do.call("rbind", soln) ## omits naming. > if (ncol(rv)==1){ rv <- as.vector(rv) ; names(rv) <- row.names(data.notdone) > } > else rownames(rv) <- row.names(data.notdone) > rv > } > > And finally, you don't even need row.names for c(v1,d[loc<1,2]) > > Or am I missing something here ? > > BTW your code uses cat.stderr (which is local ? ) instead of cat, and > has no call to multicore. > > Cheers > > > >> > On Mon, Mar 26, 2012 at 4:28 PM, ivo welch <[email protected]> wrote: >> Dear R wizards--- >> >> I have a wrapper on mclapply() that makes it a little easier for me to >> do multiprocessing. (Posting this may make life easier for other >> googlers.) I pass a data frame, a vector that tells me what rows >> should be recomputed, and the function; and I get back a vector or >> matrix of answers. >> >> d <- data.frame( id=1:6, val=11:16 ) >> loc <- c(TRUE,TRUE,FALSE,TRUE,FALSE,TRUE) >> v1 <- mc.byselectrows( d, loc, function(x) x[,2]^2 ) >> v2 <- mc.byselectrows(d, loc, function(x) cbind(x[,2]^2,x[,2]^3)) >> >> mc.byselectrows <- function(data.in, recalclist, FUN, ...) { >> >> data.notdone <- data.in[recalclist,] >> cat.stderr("[mc.byselectrows: ", nrow(data.notdone), "rows to be >> recomputed out of", nrow(data.in), "]\n") >> >> FUN.ON.ROWS <- function(.index, ...) >> as.matrix(FUN(data.notdone[.index,], ...)) >> soln <- mclapply( as.list(1:nrow(data.notdone)) , FUN.ON.ROWS, ... ) >> rv <- do.call("rbind", soln) ## omits naming. >> if (ncol(rv)==1) rv <- as.vector(rv) >> rv >> } >> >> this works fine, except that what I want to get NA's in the return >> positions that were not recalculated. then, I can write >> >> newdata$y <- ifelse ( is.na(olddata$y), mc.byselectrows( olddata, >> is.na(olddata$y), fun.calc.y ), olddata$y ) >> >> I can do this very inelegantly, of course. I can merge recalclist >> into data.in and then write a loop that substitutes for the do.call to >> rbind. yikes. or I could do the recalclist contingency inside the >> FUN.ON.ROWS, but this is costly in terms of execution time. are there >> obvious solutions? advice appreciated. >> >> regards, >> >> /iaw >> ---- >> Ivo Welch ([email protected]) >> >> ______________________________________________ >> [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 >> and provide commented, minimal, self-contained, reproducible code. ______________________________________________ [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 and provide commented, minimal, self-contained, reproducible code.
