请问这个问题怎么办？版本R-3.5.0.tar.gz

installing the source package ‘stringi’

trying URL 'http://cran.rstudio.com/src/contrib/stringi_1.2.2.tar.gz'

Content type 'application/x-gzip' length 7270627 bytes (6.9 MB)

downloaded 6.9 MB

* installing *source* package 'stringi' ...

** 成功将'stringi'程序包解包并MD5和检查

Warning in system("sh ./configure.win") : 'sh' not found

ERROR: configuration failed for package 'stringi'

* removing 'D:/program files/R language/R-3.5.0/library/stringi'

In R CMD INSTALL

Warning in install.packages :

  installation of package ‘stringi’ had non-zero exit status

The downloaded source packages are in

‘C:\Users\Michael\AppData\Local\Temp\RtmpQXf6bD\downloaded_packages’