title: Plotting sigmoid function in mathematica
body: <p>I am new to Mathematica. </p>
  
  <p>I want to write my own sigmoid function where I can give coefficients to <code>e</code> and <code>x</code>. When plotting, I don't get any output, what could be the problem?</p>
  
  <pre><code>sigmoid_f[x_, a_, b_] := 1/(1 + ae^-bx)
  Plot[sigmoid_f[x, 1, 1], {x, -5, 5}]
  </code></pre>
  
  <p>Thank you for your help!</p>