title: How to fit a specific exponential function with numpy
body: <p>I'm trying to fit a series of data to a exponential equation, I've found some great answer here: <a href="https://stackoverflow.com/questions/3433486/how-to-do-exponential-and-logarithmic-curve-fitting-in-python-i-found-only-poly">How to do exponential and logarithmic curve fitting in Python? I found only polynomial fitting</a> But it didn't contain the step forward that I need for this question.</p>
  
  <p>I'm trying to fit <em>y</em> and <em>x</em> against a equation: <em>y</em> = <em>-Ae</em><sup><em>Bx</em></sup> + <em>A</em>. The final <em>A</em> has proven to be a big trouble and I don't know how to transform the equation like <em>log(y)</em> = <em>log(A)</em> + <em>Bx</em> as if the final A was not there.</p>
  
  <p>Any help is appreciated.</p>