title: Change text on strips in lattice plots
body: <p>how do I change the text displayed in the strips of lattice plots?
  example:
  suppose I have a data frame test consisting of 3 columns</p>
  
  <pre><code>x
   [1]  1  2  3  4  5  6  7  8  9 10
  
  y
   [1] "A" "A" "A" "A" "A" "B" "B" "B" "B" "B"
  
  a
   [1] -1.9952066 -1.7292978 -0.8789127 -0.1322849 -0.1046782  0.4872866
   [7]  0.5199228  0.5626998  0.6392686  1.6604549
  </code></pre>
  
  <p>a normal call to a lattice plot </p>
  
  <pre><code>xyplot(a~x | y,data=test)
  </code></pre>
  
  <p>will give the plot with the Text 'A' and 'B' on the strips</p>
  
  <p>How can I get different texts written on the strips?</p>
  
  <p>An attept with another character vector </p>
  
  <pre><code>z
   [1] "a" "a" "a" "a" "a" "b" "b" "b" "b" "b"
  </code></pre>
  
  <p>and a call to <code>strip.custom()</code></p>
  
  <pre><code>xyplot(a~x | y,data=test,strip=strip.custom(var.name=z))
  </code></pre>
  
  <p>does not give the desired result.</p>
  
  <p>In reality it is an internationalization problem.</p>