title: Rotate axis label upside down in R base plot
body: <p>I need some help with axis labels in base R plotting, thanks in advance for any guidance!</p>
  
  <h2>What I need:</h2>
  
  <p>In <code>R</code> base <code>plot()</code> I would like to rotate my <code>axis(3, ...)</code> label to -90 degrees to get the following output:</p>
  
  <p><img src="https://i.stack.imgur.com/o9ZPi.png" alt="enter image description here"></p>
  
  <p>(note that I have rotated the pic outside R)</p>
  
  <h2>Why I need it (big picture):</h2>
  
  <p>I am using <a href="http://svitsrv25.epfl.ch/R-doc/library/Hmisc/html/labcurve.html" rel="nofollow noreferrer"><code>labcurve</code></a> for curve annotation and strangely enough for my data the annotation results are visually waay better if applied to the -90 degree rotated graph. After running <code>labcurve</code> I can rotate the resulting R-generated PDF back 90 degrees in LaTeX.</p>
  
  <h2>What I have tried:</h2>
  
  <h3>#1</h3>
  
  <p>I know that this is governed by the <code>las</code> option in <a href="http://stat.ethz.ch/R-manual/R-patched/library/graphics/html/par.html" rel="nofollow noreferrer"><code>par</code></a> with the following options:</p>
  
  <pre><code>0: always parallel to the axis [default],
  1: always horizontal,
  2: always perpendicular to the axis,
  3: always vertical.
  </code></pre>
  
  <p>However, these four options available only cover the two angles 0 and 90 degrees as either of the following:</p>
  
  <pre><code>plot(x=c(0,10), y=c(0,1), type='n', xlab='',ylab='', axes=FALSE)
  lines(x=c(0,7,7,10), y=c(0,0.33,0.67,1))
  axis(2, at=c(0,1), labels=c('',''), las=2)
  xlabels &lt;- c('0','10')
  axis(3, at=c(0,10), labels=xlabels, las=0)
  </code></pre>
  
  <p>or </p>
  
  <pre><code>axis(3, at=c(0,10), labels=xlabels, las=1)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/zyCHt.png" alt="enter image description here"></p>
  
  <pre><code>axis(3, at=c(0,10), labels=xlabels, las=2)
  </code></pre>
  
  <p>or</p>
  
  <pre><code>axis(3, at=c(0,10), labels=xlabels, las=3)
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/nK0q0.png" alt="enter image description here"></p>
  
  <h3>#2:</h3>
  
  <p>One could think of <code>str</code> but according to the doc:</p>
  
  <blockquote>
    <p>Note that string/character rotation via argument srt to par does not
    affect the axis labels.</p>
  </blockquote>
  
  <p><em>Thanks again!</em></p>