I do not quite follow your post but here are some suggestions.
1) You can the na.strings argument to simplify things df <- read.delim(file="lala.txt", na.strings="-" ) 2) If you can count the number of metastasis per row first, then find the rows with zero sum. met.cols <- c(11,12,14,21,23,24) # metastasis columns number.of.met <- rowSums( mela[ , met.cols ] == "-" ) have.no.met <- which( number.of.met == 0 ) mela.no.met <- mela[ have.no.met , ] If you had coded your "-" as NA during read in then, the second line needs to be changed to number.of.met <- rowSums( is.na( mela[ , met.cols ] ) ) or simply use complete.cases met.cols <- c(11,12,14,21,23,24) # metastasis columns mela.no.met <- mela[ which( complete.cases(mela[ , met.cols]) ) , ] 3) If you name your columns in a systematic fashion, then you can easily extract and specify those columns. For example if your columns were named cn <- c( "age", "colon.met", "PSA.level", "prostate.met", "gender", "hospitalisation.days", "status", "liver.met", "ethnicity") Then you can extract those names ending with ".met" as met.cols <- grep( "\\.met$", cn ) met.cols [1] 2 4 8 Regards, Adai On Sun, 2005-11-13 at 18:40 +0100, [EMAIL PROTECTED] wrote: > Hi i'm a french medical student, > i have some data that i import from excel. My colomn of the datafram > are the localisations of metastasis. If there is a metatsasis there is > the symbol "_". i want to exclude the row without metastasis wich > represent the NA data. > > so, i wrote this > > mela is the data fram > > mela1=ifelse(mela[,c(11:12,14:21,23,24)]=="_",1,0) # selection of the > colomn of metastasis localisation > > mela4=subset(mela3,Skin ==0 & s.c == 0 & Mucosa ==0 & Soft.ti ==0 & > Ln.peri==0 & Ln.med==0 & Ln.abdo==0 & Lung==0 & Liver==0 & > Other.Visc==0 & Bone==0 & Marrow==0 & Brain==0 & Other==0) ## selection > of the row with no metastasis localisation > nrow(mela4) > > but i dont now if it is possible to make the same thin as > ifelse(mela3,Skin & s.c== 0, 0,NA) with more than colomn and after to > exclude of my data the Na with na.omit. > > The last question is how can i omit only the row which are NA value for > the colomn metastasis c(11:12,14:21,23,24)) > > Thank you for your help > > > > Bertrand billemont > [[alternative text/enriched version deleted]] > > ______________________________________________ > 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 > ______________________________________________ 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