I guess this thread has gone on long enough, but I haven't seen anyone yet suggest what to me seems like the obvious thing if you want to do this with mutate, namely
testdata <- mutate(testdata, place = as.factor(substr(subject, 1, 3))) Best, Ista On Fri, Mar 4, 2016 at 10:45 PM, Boris Steipe <boris.ste...@utoronto.ca> wrote: > 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. ______________________________________________ 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.
