title: How to solve nested ODE equations
body: <p>We can use the <code>deSolve</code> package in R for ordinary differential equations (ODE), however, I can't find a way to solve two nested ODE equations, suppose `</p>
  
  <pre><code>b'(t) = beta - k*b(t); 
  a'(t) = alpha -b(t)*gamma;
  </code></pre>
  
  <p>where <code>'</code> means differentiation. How can we solve <code>a</code> and <code>b</code> then? as <code>a'</code> is a function of <code>b</code>, we have to solve <code>a</code> and <code>b</code> simultaneously. </p>
  
  <p>I got an error:</p>
  
  <blockquote>
    <p>Error in lsoda(y, times, func, parms, ...) :   The used combination of solvers cannot be nested.</p>
  </blockquote>
  
  <p>When I tried to add the solve for <code>b</code> inside the ode solution for <code>a</code>.</p>