title: unable to install packages("caret") completely in R version 3.2.3
body: <pre><code>&gt; require("caret")
    Loading required package: caret
    Loading required package: lattice
    Loading required package: ggplot2
    Error in loadNamespace(j &lt;- i[[1L]], c(lib.loc, .libPaths()), versionCheck =      vI[[j]]) : 
     there is no package called ‘pbkrtest’
  </code></pre>
  
  <p>So I found that there is lack of "pbkrtest" then I tried to reinstall it.</p>
  
  <pre><code>&gt; install.packages("pbkrtest")
   Installing package into ‘C:/Users/ADMIN/Documents/R/win-library/3.2’
   (as ‘lib’ is unspecified)
  
   There is a binary version available but the source version is
   later:
       binary source needs_compilation
   pbkrtest  0.4-2  0.4-3             FALSE
  
   installing the source package ‘pbkrtest’
  
  trying URL 'https://rweb.crmda.ku.edu/cran/src/contrib/pbkrtest_0.4-  3.tar.gz'
  Content type 'application/x-gzip' length 164415 bytes (160 KB)
  downloaded 160 KB
  
  * installing *source* package 'pbkrtest' ...
  ** package 'pbkrtest' successfully unpacked and MD5 sums checked
  ** R
  ** data
  ** inst
  ** preparing package for lazy loading
  Warning: replacing previous import by 'stats::sigma' when loading 'pbkrtest'
  Error : object 'sigma' is not exported by 'namespace:stats'
  ERROR: lazy loading failed for package 'pbkrtest'
  * removing 'C:/Users/ADMIN/Documents/R/win-library/3.2/pbkrtest'
  
  The downloaded source packages are in 
      ‘C:\Users\ADMIN\AppData\Local\Temp\Rtmpk7mJT0\downloaded_packages’
  Warning messages:
  1: running command '"D:/R-3.2.3/bin/x64/R" CMD INSTALL -l     
  "C:\Users\ADMIN\Documents\R\win-library\3.2"   
  
    C:\Users\ADMIN\AppData\Local\Temp\Rtmpk7mJT0/downloaded_packages/pbkrtest_0.4-  3.tar.gz' had status 1 
  2: In install.packages("pbkrtest") :
  installation of package ‘pbkrtest’ had non-zero exit status
  </code></pre>
  
  <p>It seems like that the installation keeps failing.
  As a result, I couldn't use other code using caret packages. </p>