Please help with this error message drugbook is an 885 x 32 dataframe
>names(drugbook) [1] "DRUG1" "DRUG2" "DRUG3" "DRUG4" "DRUG5" [6] "DRUG6" "DRUG7" "DRUG8" "DRUG9" "DRUG10" [11] "DRUG11" "DRUG12" "DRUG13" "DRUG14" "DRUG15" [16] "DRUG16" "DrugDose1" "DrugDose2" "DrugDose3" "DrugDose4" [21] "DrugDose5" "DrugDose6" "DrugDose7" "DrugDose8" "DrugDose9" [26] "DrugDose10" "DrugDose11" "DrugDose12" "DrugDose13" "DrugDose14" [31] "DrugDose15" "DrugDose16" Equivs is a dataframe holding information for a certain subclass of drugs > head(Equivs) Name Equiv 1 Alprazolam 0.5 2 Bromazepam 5.5 3 Chlordiazepoxide 25.0 4 Clobazam 20.0 5 Clonazepam 0.5 6 Clorazepate 15.0 What I'm trying to is for each element of drugbook, get the value in Equivs$Equiv, and multiply it by the corresponding drug dose, which will be in the n+16 th column on in the same row of drugbook. Not all of the grabbed names from Drugbook will be in the dataframe Equivs, though. So sometimes the == will return a null. i.e. DrugDose16 is the dose of Drug 16 this I think should work: ( I did try apply and got knotted, so stopped) >mydosequivalents=list() >for( c in 1:16) { for (r in 1:885){ name<-as.character(drugbook[r,c]); equivalent<-Equivs$Equiv[Equivs$Name==name]; dosequivalent<-drugbook[r,c+16] * equivalent; if (length(dosequivalent)>0) mydosequivalents[r][c]<-dosequivalent else (mydosequivalents[r][c]<-0) } } But it is throwing an error, and I can't figure out why. I remedied a previous error by checking the length of the equivalent. >warnings() .... 50: In mydosequivalents[c][r] <- dosequivalent : number of items to replace is not a multiple of replacement length mydosequivalents ends up being full of "NULL" and zeros Thanks in advance for any help Ross -- View this message in context: http://r.789695.n4.nabble.com/number-of-items-to-replace-is-not-a-multiple-of-replacement-length-tp3851265p3851265.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.