title: Writing Pandas Dataframes as well as numpy arrays to a common Excel File
body: <p>Using Python 3.6 and Pandas 0.22 I have created a pandas dataframe <code>IRdaily</code> with time series of daily changes in various interest rates. I can easily write the Pandas dataframe to Excel using the commands:</p>
  
  <pre><code>writer = pd.ExcelWriter(outFileName)
  IRdaily.to_excel(writer, 'Daily Changes')
  </code></pre>
  
  <p>But if I now compute the eigenvalue decomposition (both the vector of eigenvalues and the matrix of eigenvectors are numpy ndarrays) and try to write them to the same worksheet I get an error:</p>
  
  <pre><code>covD  = deltaIRdaily.cov()
  eigValD, eigVecD = np.linalg.eigh(covD)
  eigValD.to_excel(writer, 'Daily Changes', startcol = 15) 
  eigVecD.to_excel(writer, 'Daily Changes', startrow = 15, startcol = 15) 
  
  
  Traceback (most recent call last):
    File "c:\Documents\Python\FedInterestRateDataExtract.py", line 58, in &lt;module&gt;
      eigValD.to_excel(writer, 'Daily Changes', startcol = 15)
  AttributeError: 'numpy.ndarray' object has no attribute 'to_excel'
  </code></pre>
  
  <p>How can I write ndarrays to a specified row and column in an existing worksheet in an open workbook? It's being done correctly with Pandas dataframes, so I'm guessing that there must be a simple way in which to write the results of any analysis of the data held in a Pandas dataframe.</p>
  
  <p>Many thanks in advance for your advice and assistance</p>
  
  <p>Thomas Philips</p>