title: conditional probability plot in R
body: <p>I am new to R, and I am trying to create a conditional probability plot, with pre-test probability on the x axis and post-test probability on the y axis. Similar to the one in the link <a href="https://www.google.co.uk/search?q=conditional%20probability%20plot&amp;source=lnms&amp;tbm=isch&amp;sa=X&amp;ved=0CAcQ_AUoAWoVChMI4ILB1rGAyAIVgVsaCh1xcgyP&amp;biw=1280&amp;bih=887#imgrc=Ax1bN3WZ4LfMBM%3A" rel="nofollow">conditional probability plot</a>. I need to plot points for a positive test and join them together with a line, and plot points for a negative test and join the points together with a line, on the same graph.</p>
  
  <p>I have the data:
  Pre-test prob for negative <code>test &lt;- c(0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100)</code>
  Post-test prob for negative <code>test &lt;- c(0, 3, 7, 11, 17, 22, 30, 40, 53, 72, 100)</code>
  Pre-test prob for positive <code>test &lt; - c(0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100)</code>
  Post-test prob for positive <code>test &lt;- c(0, 38, 57, 69, 77, 83, 88, 94, 95, 98, 100)</code> </p>
  
  <p>However I am unsure how best to organise the data or of the code to produce the graph that I need! I have searched for "conditional probability plots" but haven't found anything helpful. 
  Any guidance would be much appreciated.
  Thanks, Laura </p>