# 1 grep returns an index, not the value unless you use grep(..., value = TRUE).
Easier might be: # 2 Sample2 <- substr(Sample, 1, 2) ifelse(Sample2 == "BU", "up", ifelse(Sample2 == "BM", "mid", "down")) or #3 the following which matches the first 2 characters against the given list names and return the corresponding list values. library(gsubfn) gsubfn("^(..).", list(BU = "up", BD = "down", BM = "mid"), Sample) Note that if Sample is a factor rather than character then use as.character(Sample) in place of Sample in the last line. On Sat, Apr 3, 2010 at 12:18 PM, Sam Albers <tonightstheni...@gmail.com> wrote: > Good Morning, > > I am trying to create a new column of character strings based on the first > two letters in a string in another column. I believe that I need to use some > combination of ifelse and grep but I am not totally sure how to combine > them. I am not totally sure why the command below isn't working. Obviously > it isn't finding anything that matches my criteria but I am not sure why. > Any ideas on how I might be able to modify this to get to work? Below is > also a data example of what I would like to achieve with this command. > >> section <- ifelse(Sample==grep("^BU", Sample),"up", > ifelse(Sample==grep("^BM", Sample), "mid","down")) >> section > [1] "down" "down" "down" "down" "down" "down" "down" "down" "down" "down" > [11] "down" "down" > > Thanks in advance. > > Sam > > Sample Transmission section BU1 0.39353 up BU2 0.38778 up BU3 0.42645 up > BM1 0.37510 mid BM2 0.5103 mid BM3 0.67224 mid BD1 0.37482 down BD2 > 0.54716 down BD3 0.50866 down BU1 0.34869 up BU2 0.32831 up BU3 0.59877 > up BM1 0.52518 mid BM2 0.94387 mid BM3 0.94387 mid BD1 0.46872 down BD2 > 0.63115 down BD3 0.45239 down > n" "down" "down" "down" "down" "down" "down" > > > > > -- > ***************************************************** > Sam Albers > Geography Program > University of Northern British Columbia > 3333 University Way > Prince George, British Columbia > Canada, V2N 4Z9 > phone: 250 960-6777 > ***************************************************** > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. > ______________________________________________ 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.