Functions exported from nlme to implement fixest methods
The package fixest uses the fixef method from nlme. Unfortunately, re-exporting this method is required in order not to attach package nlme.
Here is the help from package nlme: fixef. The help from package fixest is here: fixef.fixest.
I could find this workaround thanks to the package plm.
Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.