title: Variables in NumPy
body: <p>In NumPy, I'm trying to represent differential equations of the form: <code>y' = p(t)y + g(t)</code>, where <code>p(t)</code> is an nxn matrix and and <code>g(t)</code> is an nx1 matrix. Something like:</p>
  
  <pre><code>y' = [[1,5], [2,1]] + [[e^t], [1]]
  </code></pre>
  
  <p>I know how to represent matrices in NumPy, but how would I represent matrices that contain variables (for example, <code>2t</code> or <code>e^t</code>)?</p>