title: merging tweets by date
body: <p>I hope this is not to basic a question,
  I have a dataframe of tweets (in R).
  My aim is to calculate the sentiment by date.</p>
  
  <p>I would be so grateful if anyone would advise me,
  how to concatenate tweets <code>tweet$text</code> by date, where 
  each observation becomes a string of merged tweets/text</p>
  
  <p>For example, if I had:</p>
  
  <pre><code>Created_Date       Tweet
  
  2014-01-04         "the iphone is magnificent"
  
  2014-01-04         "the iphone's screen is poor"
  
  2014-01-04         "I will always use Apple products"
  
  2014-01-03         "iphone is overpriced, but I love it"
  
  2014-01-03         "Siri is very sluggish"
  
  2014-01-03         "iphone's maps app is poor compared to Android"
  </code></pre>
  
  <p>I would like a loop/function to merge the tweets by Created_Date
  resulting in something like this</p>
  
  <pre><code>Created_Date       Tweet
  
  2014-01-04         "the iphone is magnificent", "the iphone's screen is poor",              "I will always use Apple products"
  
  2014-01-03         "iphone is overpriced, but I love it", "Siri is very sluggish", "iphone's maps app is poor compared to Android"
  </code></pre>
  
  <p>Here are my data</p>
  
  <pre><code> dat &lt;-   structure(list(Created_Date = structure(c(1388793600, 1388793600, 
      1388793600, 1388707200, 1388707200, 1388707200), class = c("POSIXct", 
      "POSIXt"), tzone = "UTC"), Tweet = c("the iphone is magnificent", 
      "the iphone's screen is poor", "I will always use Apple products", 
      "iphone is overpriced, but I love it", "Siri is very sluggish", 
      "iphone's maps app is poor compared to Android")), .Names = c("Created_Date", 
      "Tweet"), class = c("tbl_df", "tbl", "data.frame"), row.names = c(NA, 
      -6L))
  </code></pre>