You mean this? test$place <- factor(test$place) You can create a new column in a data frame by assigning something to it. E.g. test$pollywog <- 1:6 ... creates that column in "test".
But factor(test$place) was empty, because no such column previously existed, like: R > factor(test$barbapapa) factor(0) Levels: So the right hand side has 0 rows, but the left hand side needs six. Of course you could create your column directly: R > str(test) 'data.frame': 6 obs. of 6 variables: $ subject: Factor w/ 6 levels "001-002","002-003",..: 1 2 3 4 5 6 $ group : Factor w/ 2 levels "boys","girls": 1 1 1 2 2 2 $ wk1 : int 2 7 9 5 2 1 $ wk2 : int 3 6 4 7 6 4 $ wk3 : int 4 5 6 8 3 7 $ wk4 : int 5 4 1 9 8 4 R > test$place <- factor(substr(test$subject,1,3)) # here's were it gets done R > str(test) 'data.frame': 6 obs. of 7 variables: $ subject: Factor w/ 6 levels "001-002","002-003",..: 1 2 3 4 5 6 $ group : Factor w/ 2 levels "boys","girls": 1 1 1 2 2 2 $ wk1 : int 2 7 9 5 2 1 $ wk2 : int 3 6 4 7 6 4 $ wk3 : int 4 5 6 8 3 7 $ wk4 : int 5 4 1 9 8 4 $ place : Factor w/ 6 levels "001","002","003",..: 1 2 3 4 5 6 ... it's just that you insisted on mutate(). Cheers, Boris On Mar 4, 2016, at 9:31 PM, KMNanus <kmna...@gmail.com> wrote: > Boris - > > Boy, do I feel dumb - that’s exactly what I wanted. I’ve tried this every > way I can think of without assigning the result to the original name of the > data frame. I was trying to assign the result to a variable (test$place). > > Can u pls explain to me why assigning the result to the new variable was > wrong? > > BTW, really appreciate your help. > > Ken > kmna...@gmail.com > 914-450-0816 (tel) > 347-730-4813 (fax) > > <image001.jpg> > >> On Mar 4, 2016, at 9:21 PM, Boris Steipe <boris.ste...@utoronto.ca> wrote: >> >> LOL you still need to assign it though: >> >> >> test <- mutate(test, place = factor(substr(test$subject,1,3))) >> >> str(test) >> 'data.frame': 6 obs. of 7 variables: >> $ subject: Factor w/ 6 levels "001-002","002-003",..: 1 2 3 4 5 6 >> $ group : Factor w/ 2 levels "boys","girls": 1 1 1 2 2 2 >> $ wk1 : int 2 7 9 5 2 1 >> $ wk2 : int 3 6 4 7 6 4 >> $ wk3 : int 4 5 6 8 3 7 >> $ wk4 : int 5 4 1 9 8 4 >> $ place : Factor w/ 6 levels "001","002","003",..: 1 2 3 4 5 6 >> >> >> Without assigning the result, the output only gets printed to console. >> Remember that R is a functional language - a properly written R functio does >> not change anything, it only returns its result. >> >> :-) >> >> >> On Mar 4, 2016, at 4:13 PM, KMNanus <kmna...@gmail.com> wrote: >> >>> If I call mutate this way - mutate(test, place = >>> factor(substr(test$subject,1,3))), I get the same output as above but when >>> I call class(test$place), I get NULL and the variable disappears. >> > ______________________________________________ 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.
