title: how can I plot a Cox model with ~pspline and find the cutoff in R?
body: <p>I am now learning how to evaluate a non-linear association between X and Y. And I find package 'smoothHR' is a good choice.
  for example, I want to evaluate the non-linear association between HDLC and event</p>
  <pre><code>model&lt;-coxph(Surv(futime, death) ~ age+sex+pspline(hdlc,df = 2), data = data,x=T)
  hr1 &lt;- smoothHR(data=data, coxfit=model)
  print(hr1)
  plot(hr1,predictor='hdlc',prob = 0,conf.level=0.95,round.x = 1)
  </code></pre>
  <p>finally, I get a plot like:</p>
  <p><img src="https://i.stack.imgur.com/3Ft5c.png" alt="this" /></p>
  <p>And I have 2 questions</p>
  <ol>
  <li>How can I change Y aixs to Hazard ratio (HR)</li>
  <li>How can I find the optimal cutoff——the intersection of 95% confident interval curve and the line y = 1</li>
  </ol>
  <p>just like:</p>
  <p><img src="https://i.stack.imgur.com/HbsH2.png" alt="this" /></p>
  <p>and</p>
  <p><img src="https://i.stack.imgur.com/L6jKH.png" alt="this" /></p>
  <p>Thank you!</p>