set（new）中的错误：在安装SOfun时无法更改工作目录

Question

我想在我的新R 3.1.2上安装SOfun软件包，但它已停止，并显示如下错误。

devtools::install_github("mrdwab/SOfun")

WARNING: Rtools is required to build R packages, but no version of Rtools compatible with R 3.1.2 was found. (Only the following incompatible version(s) of Rtools were found:3.2)

Please download and install Rtools 3.1 from http://cran.r-project.org/bin/windows/Rtools/ and then run find_rtools().
Downloading github repo mrdwab/SOfun@master
Installing SOfun

Error in set(new) : cannot change working directory

我很感激任何解决此错误的建议。