title: Numpy python find minimum value of each column and subtract this value from each column
body: <p>Can anyone help with a snippet of code using numpy and python?</p>
  
  <p>Given an numpy array such as </p>
  
  <pre><code>a = array([[1,11], [3,9], [5,7]]
  </code></pre>
  
  <p>I want to find the minimun value of each column, so 1 and 7 and then subtract this value from the respective columns,  </p>
  
  <pre><code>a = array([[0,4], [2,2], [4,0]]
  </code></pre>