title: Install package in R: 'stdlib.h' file not found
body: <p>I am trying to install RMark from RStudio. I notice that one of the packages required could not be installed. It seems there are some issues with C. Can you help me? </p>
  
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  <pre class="snippet-code-html lang-html prettyprint-override"><code>&gt; install.packages('mvtnorm')
  trying URL 'https://cran.rstudio.com/src/contrib/mvtnorm_1.0-8.tar.gz'
  Content type 'application/x-gzip' length 159539 bytes (155 KB)
  ==================================================
  downloaded 155 KB
  
  During startup - Warning messages:
  1: Setting LC_CTYPE failed, using "C" 
  2: Setting LC_TIME failed, using "C" 
  3: Setting LC_MESSAGES failed, using "C" 
  4: Setting LC_MONETARY failed, using "C" 
  * installing *source* package 'mvtnorm' ...
  ** package 'mvtnorm' successfully unpacked and MD5 sums checked
  ** libs
  x86_64-apple-darwin13.4.0-clang -I"/anaconda3/lib/R/include" -DNDEBUG   -D_FORTIFY_SOURCE=2 -mmacosx-version-min=10.9 -I/anaconda3/include   -fPIC  -march=core2 -mtune=haswell -mssse3 -ftree-vectorize -fPIC -fPIE -fstack-protector-strong -O2 -pipe -I/anaconda3/include -fdebug-prefix-map==/usr/local/src/conda/- -fdebug-prefix-map==/usr/local/src/conda-prefix  -c C_FORTRAN_interface.c -o C_FORTRAN_interface.o
  In file included from C_FORTRAN_interface.c:8:
  In file included from ./mvtnorm.h:2:
  /anaconda3/lib/R/include/R.h:55:11: fatal error: 'stdlib.h' file not found
  # include &lt;stdlib.h&gt; /* Not used by R itself, but widely assumed in packages */
            ^~~~~~~~~~
  1 error generated.
  make: *** [/anaconda3/lib/R/etc/Makeconf:160: C_FORTRAN_interface.o] Error 1
  ERROR: compilation failed for package 'mvtnorm'
  * removing '/anaconda3/lib/R/library/mvtnorm'
  Warning in install.packages :
    installation of package 'mvtnorm' had non-zero exit status
  
  The downloaded source packages are in
   '/private/var/folders/5m/lbpq3yj53n7clgx4r1fy6blr0000gn/T/RtmppNGt3S/downloaded_packages'
  Updating HTML index of packages in '.Library'
  Making 'packages.html' ... done
  &gt; </code></pre>
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