title: Error when installing an R package from github: Could not find build tools necessary to build data.table
body: <p>From within RStudio I'm trying to install the data.table package from github following <a href="https://stackoverflow.com/a/9656182/4945268">these instructions</a>, and the package seems to download without a problem:</p>
  
  <pre><code>&gt; library(devtools)
  &gt; dev_mode(on=T)
  Dev mode: ON
  d&gt; install_github("Rdatatable/data.table")
  Downloading GitHub repo Rdatatable/data.table@master
  from URL https://api.github.com/repos/Rdatatable/data.table/zipball/master
  </code></pre>
  
  <p>I then receive the following prompt:</p>
  
  <blockquote>
    <p>Building R package from source requires installation of additional
    build tools.  Do you want to install the additional tools now?</p>
  </blockquote>
  
  <p>Selecting "Yes" results in this error message:</p>
  
  <pre><code>Error: Could not find build tools necessary to build data.table
  </code></pre>
  
  <p>Thinking this might be an RStudio problem, I tried installing the package in the standard R console, but this also resulted in an error:</p>
  
  <pre><code>Downloading GitHub repo Rdatatable/data.table@master
  from URL https://api.github.com/repos/Rdatatable/data.table/zipball/master
  Installing data.table
  "C:/PROGRA~1/R/R-33~1.0/bin/x64/R" --no-site-file --no-environ --no-save  \
    --no-restore --quiet CMD INSTALL  \
    "C:/Users/Robert/AppData/Local/Temp/RtmpOOKOKu/devtools246832c52ab/Rdatatable-data.table-4348ff4"  \
    --library="C:/Users/Robert/Documents/R-dev" --install-tests 
  
  * installing *source* package 'data.table' ...
  ** libs
  c:/Rtools/mingw_64/bin/gcc  -I"C:/PROGRA~1/R/R-33~1.0/include" -DNDEBUG     -I"d:/Compiler/gcc-4.9.3/local330/include"  -fopenmp   -O2 -Wall  -std=gnu99 -mtune=core2 -c assign.c -o assign.o
  c:/Rtools/mingw_64/bin/gcc: not found
  make: *** [assign.o] Error 127
  Warning: running command 'make -f "Makevars" -f "C:/PROGRA~1/R/R-33~1.0/etc/x64/Makeconf" -f "C:/PROGRA~1/R/R-33~1.0/share/make/winshlib.mk" SHLIB="data.table.dll" WIN=64 TCLBIN=64 OBJECTS="assign.o bmerge.o chmatch.o dogroups.o fastmean.o fcast.o fmelt.o forder.o frank.o fread.o fwrite.o gsumm.o ijoin.o init.o openmp-utils.o quickselect.o rbindlist.o reorder.o shift.o subset.o transpose.o uniqlist.o vecseq.o wrappers.o"' had status 2
  ERROR: compilation failed for package 'data.table'
  * removing 'C:/Users/Robert/Documents/R-dev/data.table'
  Error: Command failed (1)
  d&gt;
  </code></pre>
  
  <p>I found three related posts on SO:</p>
  
  <p><a href="https://stackoverflow.com/questions/35096233/error-could-not-find-build-tools-necessary-to-build-dplyr">Error: Could not find build tools necessary to build dplyr</a></p>
  
  <p><a href="https://stackoverflow.com/questions/35914339/error-could-not-find-build-tools-necessary-to-build">Error : Could not find build tools necessary to build</a></p>
  
  <p><a href="https://stackoverflow.com/questions/36002510/could-not-find-build-tools-necessary-facing-error-with-devtools">Could not find build tools necessary . Facing error with devtools</a></p>
  
  <p>The first two seem specific to Apple OS, and the third suggests an error specific to devtools, but I don't know if that's the source of the error I'm seeing.</p>
  
  <p>Any help would be appreciated.  I'm running R version 3.3.0 in Windows 10.</p>