Thanks a lot Gabor, that was very helpful. All sorted now! Best
David > Your columns are factors, not character strings. Use as.is = TRUE as > an argument to read.table. Also its a bit dangerous to use T although > not wrong. Its safer to use TRUE. > > On 9/7/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > Dear List, > > > > I have a newbie question. I have read in a data.frame as follows: > > > > > data = read.table("table.txt", header = T) > > > data > > X1 X2 X3 X4 > > A AB AC AB AC > > B AB AC AA AB > > C AA AB AA AB > > D AA AB AB AC > > E AB AA AA AB > > F AB AA AB AC > > B AB AC AB AA > > > > I would like to replace AA values by BB in column X2. I have tried > > using replace() with no success, although I am not sure this is the > > right function. This is the code I have used: > > > > data$X2 <- replace(data$X2, data$X2 =="AA","BB") > > Warning message: > > invalid factor level, NAs generated in: `[<-.factor`(`*tmp*`, list, > > value = "BB") > > > > What is wrong with the code? How can I get this done? how about > > changing AA values by BB in all 4 columns simultaneously? Actually > > this is a small example dataframe, the real one would have about 1000 > > columns. > > > > Extendind this, I found a similar thread dated July 2006 that used > > replace() on iris dataset, but I have tried reproducing it obtaining > > same warning message > > > > iris$Species <- replace(iris$Species, iris$Species > > == "setosa","NewName") > > Warning message: > > invalid factor level, NAs generated in: `[<-.factor`(`*tmp*`, list, > > value = "NewName") > > > > Thanks in advance your help, > > > > David > > > > ______________________________________________ > > 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 > > and provide commented, minimal, self-contained, reproducible code. > > > ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.