Tried your code. Here's what I got:
install.packages("installr")
Installing package into ‘C:/Users/Admin/Documents/R/win-library/3.3’
(as ‘lib’ is unspecified)
trying URL 'https://mran.revolutionanalytics.com/snapshot/2016-11-01/bin/windows/contrib/3.3/installr_0.17.8.zip'
Content type 'application/zip' length 244913 bytes (239 KB)
downloaded 239 KB
package ‘installr’ successfully unpacked and MD5 sums checked
The downloaded binary packages are in
C:\Users\Admin\AppData\Local\Temp\RtmponLu5l\downloaded_packages
> library(installr)
Welcome to installr version 0.17.8
More information is available on the installr project website:
https://github.com/talgalili/installr/
Contact: <tal.galili@gmail.com>
Suggestions and bug-reports can be submitted at: https://github.com/talgalili/installr/issues
To suppress this message use:
suppressPackageStartupMessages(library(installr))
> updateR()
Error in loadNamespace(i, c(lib.loc, .libPaths()), versionCheck = vI[[i]]) :
there is no package called ‘stringi’