Since you did not provide sample data (use dput instead of posting links to 'jpg' files), you can probably do it without loops:
k=resp[,5] CO2umol <- resp[,6]*((Press*infoch[k,11]*1e-6)/(R*(resp[,7]+273.15))) CO2v <- CO2umol/(infoch[k,10]) CO2s <- CO2umol/(infoch[k,9] On Mon, Nov 12, 2012 at 12:39 PM, Charles D. <charlybeg...@live.fr> wrote: > Hello , > > I'm new to R and don't really understand how to use the function "apply" > instead of a "for loop", particularly for a function with multiple entries. > I have a big data file and would like to apply a function in multi thread to > accelerate the processus. > > I have a data frame containing values of* CO2 in ppm (resp[i,6])* that I > want to convert in umol of CO2 emitted by stem volume biomass (CO2v) and > stem area (CO2s). (tree respiration) > > The loop that I have is calculating the CO2 fluxes for each row. > > *Script :* > for (i in 1:nrow(resp)) { > k=resp[i,5] > CO2umol[i]<-resp[i,6]*((Press*infoch[k,11]*1e-6)/(R*(resp[i,7]+273.15))) > CO2v[i]<-CO2umol[i]/(infoch[k,10]) > CO2s[i]<-CO2umol[i]/(infoch[k,9]) > } > > For that, I have two data frames : > - *infoch :* variables used to calculate CO2 fluxes (16 rows with the > characteristics of 16 analysis chambers) > > <http://r.789695.n4.nabble.com/file/n4649326/infoch.jpg> > > - *resp: *time series containing CO2 values and temperatures by chamber > analysed (more than 500.000 rows) > > <http://r.789695.n4.nabble.com/file/n4649326/resp.jpg> > > other variables : > Press=93000 > R=8.31 > > The loop is working good, but taking quite a long time to process, if > someone could explain me how to use the apply function in this case, it > would be really helpful. > > Thanks > Charles > > > > -- > View this message in context: > http://r.789695.n4.nabble.com/Using-apply-instead-of-for-loop-multithreading-tp4649326.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. -- Jim Holtman Data Munger Guru What is the problem that you are trying to solve? Tell me what you want to do, not how you want to do it. ______________________________________________ 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.