title: python make correlation matrix
body: <p>I have one dataframe as below:</p>
  
  <pre><code>  combination      qmin      qmax      mean    median
  0     003-124  0.014039  0.309451  0.165592  0.169842
  0     014-017  0.992299  0.998932  0.996361  0.997515
  0     014-018  0.798309  0.966721  0.903433  0.932848
  0     014-019  0.798313  0.966721  0.903433  0.932848
  </code></pre>
  
  <p>.......................................................
  This means the factor003 and factor124 correlation coefficient is 0.165592(column mean),etc. Now I want to get the big correlation matrix,inculding all the factors. How can I get this? Thanks.</p>