Negation of sigmoid function in R

Question

I would like to use the sets package for fuzzify and defuzzify in RStudio and, in particular, the negation of the sigmoid function in a fuzzy_partition environment. For instance, this code:

weather = fuzzy_partition(varnames = c(bad = 40, ok = 65, perfect = 80),
                        FUN = fuzzy_sigmoid)

works perfectly but I would like to have something like:

weather = fuzzy_partition(varnames = c(bad = 40, ok = 65, perfect = 80),
                        FUN = 1-fuzzy_sigmoid)

that is, the negation of the sigmoid, which does not work.

I am lacking a full manual of this staff, in fact. Thank you.