duplicated factor labels.
Hi Paul, Now I see what you're getting at. I misread your original mail completely. So we definitely agree, and wholeheartedly even. The use case you just gave, is definitely in my top 5 of frustrations about R. I would like to be able to assign the same label to multiple levels without having to use eg dplyr::recode_factor() or some other vectorized switch statement to recode all data first. I understand "it's been like that 25 years", but I've looked hard to find a use case where adding this behaviour would invalid existing code and couldn't come up with something. So I add my (totally insignificant) vote for adding the possibility of assigning the same label to multiple levels in factor() itself. Cheers and thank you for bringing this up!
On Fri, Jun 16, 2017 at 6:02 PM, Paul Johnson <pauljohn32 at gmail.com> wrote:
On Fri, Jun 16, 2017 at 2:35 AM, Joris Meys <jorismeys at gmail.com> wrote:
To extwnd on Martin 's explanation : In factor(), levels are the unique input values and labels the unique
output
values. So the function levels() actually displays the labels.
Dear Joris
I think we agree. Currently, factor insists both levels and labels be
unique.
I wish that it would not accept nonunique labels. I also understand it
is impractical to change this now in base R.
I don't think I succeeded in explaining why this would be nicer.
Here's another example. Fairly often, we see input data like
x <- c("Male", "Man", "male", "Man", "Female")
The first four represent the same value. I'd like to go in one step
to a new factor variable with enumerated types "Male" and "Female".
This fails
xf <- factor(x, levels = c("Male", "Man", "male", "Female"),
labels = c("Male", "Male", "Male", "Female"))
Instead, we need 2 steps.
xf <- factor(x, levels = c("Male", "Man", "male", "Female"))
levels(xf) <- c("Male", "Male", "Male", "Female")
I think it is quirky that `levels<-.factor` allows the duplicated
labels, whereas factor does not.
I wrote a function rockchalk::combineLevels to simplify combining
levels, but most of the students here like plyr::mapvalues to do it.
The use of levels() can be tricky because one must enumerate all
values, not just the ones being changed.
But I do understand Martin's point. Its been this way 25 years, it
won't change. :).
Cheers Joris
-- Paul E. Johnson http://pj.freefaculty.org Director, Center for Research Methods and Data Analysis http://crmda.ku.edu To write to me directly, please address me at pauljohn at ku.edu.
Joris Meys Statistical consultant Ghent University Faculty of Bioscience Engineering Department of Mathematical Modelling, Statistics and Bio-Informatics tel : +32 (0)9 264 61 79 Joris.Meys at Ugent.be ------------------------------- Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php [[alternative HTML version deleted]]