title: lattice levelplot only fails under RApache
body: <p>I'm working on a PHP web app that calls R through curl and RApache.  Most things work fine. But one lattice plot throws this error:</p>
  
  <blockquote>
    <p>RApache Warning/Error!!!Error in uy +
    c(-1, 1) : non-numeric argument to
    binary operator</p>
  </blockquote>
  
  <p>I tried saving the data structures that feed into the plot and doing the plot in my local R, but then the plot works just fine. So I can't replicate the error.</p>
  
  <p>These are the loaded libraries when the script runs in RApache:</p>
  
  <pre><code>library(Brew)
  library(Cairo)
  library(rjson)
  library(DBI)
  library(RMySQL)
  library(reshape)
  library(plyr)
  library('RColorBrewer')
  library(ggplot2)
  library(lattice)
  library(latticeExtra)
  library(hexbin)
  </code></pre>
  
  <p>Here is a bit of the script:</p>
  
  <pre><code>colgrad.pal&lt;-colorRampPalette(brewer.pal(11,'Spectral'), interpolate='spline')
  
  //problem plot
  dists.med.lplot&lt;-levelplot(value~starttime+groupname|dists, data=MDist.median,
    col.regions=rev(colgrad.pal(200)),colorkey=list(col=rev(colgrad.pal(200))),
    xlab='Time(s)',ylab='Treatment',
    main='Level Plot of Median Distance',
    layout=c(1,3))
  </code></pre>
  
  <p><del>And here is a link to a datafile.  I read it in like this:</del> //link appears untrustworthy, so removed</p>
  
  <p>Data looks like this:</p>
  
  <pre><code>'data.frame':   2880 obs. of  6 variables:
   $ groupname: Factor w/ 8 levels "rowA","rowB",..: 1 1 1 1 1 1 1 1 1 1 ...
   $ fCycle   : Factor w/ 6 levels "Cycle 1","Cycle 2",..: 6 6 6 6 6 6 6 6 6 6 ...
   $ fPhase   : Factor w/ 2 levels "Dark","Light": 1 1 1 1 1 1 1 1 1 1 ...
   $ starttime: int  0 60 120 180 240 300 360 420 480 540 ...
   $ dists    : Factor w/ 3 levels "inadist","lardist",..: 1 1 1 1 1 1 1 1 1 1 ...
   $ value    : num  47.5 64 78.3 39.2 53.7 ...
  </code></pre>
  
  <p>Any ideas on what the problem is or how to better troubleshoot this?</p>
  
  <p>ETA version/platform info</p>
  
  <pre><code>        [platform] =&gt; sparc-sun-solaris2.10
          [arch] =&gt; sparc
          [os] =&gt; solaris2.10
          [system] =&gt; sparc, solaris2.10
          [status] =&gt; 
          [major] =&gt; 2
          [minor] =&gt; 10.1
          [year] =&gt; 2009
          [month] =&gt; 12
          [day] =&gt; 14
          [svn rev] =&gt; 50720
          [language] =&gt; R
          [version.string] =&gt; R version 2.10.1 (2009-12-14)
  </code></pre>