title: R: self-starting function SSasymp with known parameter?
body: <p>I want to fit an asymptotic model as follow:</p>
  
  <p>y(x) = Asym + (R0 - Asym) * exp(-exp(lrc) * x)</p>
  
  <p>The model could be fitted in R using nls() function:</p>
  
  <pre><code>y &lt;- c(22.180,21.941,21.786,21.724,20.964,19.128,18.371,17.508,16.931)
  x &lt;- c(1,3,5,9,18,36,72,144,288)
  
  nls(y ~ SSasymp(x, Asym, R0, lrc))
  </code></pre>
  
  <p>However, if I know the value of R0 (for example R0 = 25), then how can I fit this model with the self-starting function SSasymp?</p>