title: How can I change XTS to data.frame and keep Index?
body: <p>I have an XTS timeseries in R of the following format and am trying to do some processing, subsetting and re-arranging before exporting as a CSV for work in another program.</p>
  
  <pre><code>head(master_1)
                     S_1
  2010-03-03 00:00:00 2.8520
  2010-03-03 00:30:00 2.6945
  2010-03-03 01:00:00 2.5685
  2010-03-03 01:30:00 2.3800
  2010-03-03 02:00:00 2.2225
  2010-03-03 02:30:00 2.0650
  </code></pre>
  
  <p>and</p>
  
  <pre><code>str(master_1)
  An ‘xts’ object from 2010-03-03 to 2010-05-25 08:30:00 containing:
    Data: num [1:4000, 1] 2.85 2.69 2.57 2.38 2.22 ...
   - attr(*, "dimnames")=List of 2
    ..$ : NULL
    ..$ : chr "S_1"
    Indexed by objects of class: [POSIXt,POSIXct] TZ: 
    Original class: 'zoo'  
    xts Attributes:  
  List of 1
   $ dateFormat: chr "Date"
  </code></pre>
  
  <p>And I would like to convert this to a data.frame so I can manipulate it more easily and then export to another program. However, when I use <code>test1 &lt;- as.data.frame(master_1)</code> the test1 does have the Index (i.e. the dates and times) visible,</p>
  
  <pre><code>head(test1)
                         S_1
  2010-03-03 00:00:00 2.8520
  2010-03-03 00:30:00 2.6945
  2010-03-03 01:00:00 2.5685
  2010-03-03 01:30:00 2.3800
  2010-03-03 02:00:00 2.2225
  2010-03-03 02:30:00 2.0650 
  </code></pre>
  
  <p>But the Index is not shown, </p>
  
  <pre><code>str(test1)
  'data.frame': 4000 obs. of  1 variable:
   $ S_1: num  2.85 2.69 2.57 2.38 2.22 ...
  </code></pre>
  
  <p>And writing a csv <code>write.csv(master_1, file="master_1.csv")</code> does not include the time or date. Why is this, and how can I include the data/time data as a column, so it is used in other R commands and exported properly?</p>
  
  <p>Thanks for any help.</p>