Thank you all. So that I look up the relevant Help topic more fully, the part that extracts the columns of interest: [, c(1, 3:4)]
is this an instance of ?Subscript which Charles directs me to? Cheers, Aaron Bill.Venables wrote: > > Suppose you want to select column 1, 3 and 4 only. > > ### you don't need the cbind(...) here > Data1 <- data.frame(I1 = 3, I2 = c(0, 3:1, 2:5, NA), > I3 = c(1:4, NA, 5:2), I4 = 2, I5 = 3) > > Data1$mean_134 <- rowMeans(Data1[, c(1, 3:4)], na.rm = TRUE) > Data1 > > Bill Venables. > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > On Behalf Of aaront > Sent: Monday, 26 November 2007 6:02 AM > To: r-help@r-project.org > Subject: [R] rowMean, specify subset of columns within Dataframe? > > > I would like to calculate the mean of tree leader increment growth over > 5 > years (I1 through I5) where each tree is a row and each row has 5 > columns. > So far I have achieved this using rowMeans when all columns are numeric > type > and used in the calculation: > > Data1 <- data.frame(cbind(I1 = 3, I2 = c(0,3:1, 2:5,NA), I3 > =c(1:4,NA,5:2),I4=2,I5=3)) > Data1 > Data1$mean_5 <- rowMeans(Data1, na.rm =T) > Data1 > > My real dataset has many columns including several Factor type. Is it > possible to specify a range of columns within a data frame using > rowMeans > dims= (say where there is a one > Factor column called Species leading I1 to I5, and one Factor column > called > Moisture following, so 7 columns total) , or do I either need to extract > those columns to a new data frame, calculate means, and reattach to the > original data frame, or use a different function such as apply? > > Unfortunately I am fairly new to R and have a difficult time with some > terminology and concepts in R Help. > > -- > View this message in context: > http://www.nabble.com/rowMean%2C-specify-subset-of-columns-within-Datafr > ame--tf4871420.html#a13939204 > 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. > > ______________________________________________ > 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. > > -- View this message in context: http://www.nabble.com/rowMean%2C-specify-subset-of-columns-within-Dataframe--tf4871420.html#a13941498 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.
