r: package arm: error when loading: Functions found when exporting methods from the namespace ‘arm’ which are not S4 generic: ‘fixef’, ‘ranef’

Question

> library(arm)
Loading required package: lme4
Loading required package: RcppEigen
Loading required package: R2WinBUGS
Loading required package: foreign
Error : Functions found when exporting methods from the namespace ‘arm’ which are not S4 generic: ‘fixef’, ‘ranef’
Error: package/namespace load failed for ‘arm’

maybe relevant: R version is 2.15.3. arm version is 1.6-05. lme4 version is 0.99999911-1. I did run update.packages() before posting.

I am currently wondering if the latest version of arm and lme4 are not compatible. I want to use the predict.mermod() function in the new lme4 but I also rely on arm when using lme4. I tried loading arm with lme4 detached but lme4 is a required package for arm so that did not work either. Thank you for your help!

Answer 1

The current version of arm is not compatible with the development version of lme4 from R-forge/GitHub. I presume arm still expects lme4 to produce mer classes, instead of the new merMod ones.

(Side note: The latest car from R-forge (2.0-19) does support merMod classes for eg Anova(), I found out today (just in case you need it))