title: A three-parameter Pareto distribution in scipy.stats
body: <p>I am trying to define a Pareto distribution using <code>scipy.stats.pareto</code>, but the model I am using is in a quite different form which has three parameter, where <code>f(x) = (gamma(alpha + k) * lambda**alpha * x**(k - 1)) / (gamma(alpha) * gamma(k) * (lambda + x)**(alpha + k))</code>.</p>
  
  <p>I have also tried to set <code>k = 1</code> in order to reduce the distribution to a 2-parameter distribution, where <code>f(x) = (alpha * lambda**alpha) / (lambda + x)**(alpha + 1)</code>. However, I am still unable to put the parameter into <code>scipy.stats.pareto</code>.</p>
  
  <p>I have created a case where <code>alpha = 6.54545</code> and <code>lambda = 2772.72727</code> which should give a <code>mean = 500</code> and <code>std = 600</code>, but what I got was <code>Mean = 3272.7276793445976</code> and <code>std = 600.0005828803438</code>. I know this is caused by a different version of pdf, but I want to know if it is possible to use the <code>scipy.stats.pareto</code> function or any built-in function instead of writing up a new function for this distribution. </p>