Hi Lily, You're on the right track, but you should define a new column first (filled with NA values), then specify the precise rows and columns on both the left and right hand sides of the assignment operator that will be altered. Luckily, this is pretty easy...just remember to use which() on the right hand side of the assignment operator to get the index of the rows you want. Example below for "product1":
> DF$product1_1 <- NA > DF[DF$month == 1, "product1_1"] <- DF[which(DF$month == 1), "product1"]*3.1 > HTH, Bill. William Michels, Ph.D. On Mon, May 22, 2017 at 9:56 PM, lily li <chocol...@gmail.com> wrote: > Hi R users, > > I have a question about manipulating the dataframe. I want to create a new > dataframe, and to multiply rows with different seasons for different > constants. > > DF > year month day product1 product2 product3 > 1981 1 1 18 56 20 > 1981 1 2 19 45 22 > 1981 1 3 16 48 28 > 1981 1 4 19 50 21 > 1981 2 1 17 49 25 > 1981 2 2 20 47 23 > 1981 2 3 21 52 27 > > For example, how to multiply product1 in month1 by 3.1, and to multiply > product3 in month2 by 2.0? I wrote the code like this but does not work. > Thanks for your help. > > DF['month'==1, ]$product1_1 = DF['month'==1, ]$product1 * 3.1; > DF['month'==2, ]$product3_1 = DF['month'==1, ]$product3 * 2.0; > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.
