title: How to add numpy matrix as new columns for pandas dataframe?
body: <p>I have a  <code>NxM</code> dataframe and a <code>NxL</code> numpy matrix. I'd like to add the matrix to the dataframe to create L new columns by simply appending the columns and rows the same order they appear. I tried <code>merge()</code> and <code>join()</code>, but I end up with errors:</p>
  
  <blockquote>
    <p><code>assign() keywords must be strings</code> </p>
  </blockquote>
  
  <p>and </p>
  
  <blockquote>
    <p><code>columns overlap but no suffix specified</code></p>
  </blockquote>
  
  <p>respectively.</p>
  
  <p>Is there a way I can add a numpy matrix as dataframe columns?</p>