title: How to add only missing Dates in Dataframe
body: <p>I have below mentioned data frame:</p>
  
  <pre><code>Date        Val1     Val2
  2018-04-01  125      0.05
  2018-04-03  458      2.99
  2018-04-05  354      1.25
  </code></pre>
  
  <p>I want to add only missing dates considering <code>Sys.Date()</code> (Here for example <code>Sys.Date()</code> is 2018-04-06) in dataframe with corresponding val1 and val2 as 0.</p>
  
  <p>I have tried: </p>
  
  <pre><code>t2&lt;-merge(data.frame(Date= seq(min(ymd(t1$Date)), max(ymd(date)), by = "days")), t1, by = "Date", all = TRUE)
  </code></pre>
  
  <p>Required Dataframe:</p>
  
  <pre><code>Date        Val1     Val2
  2018-04-01  125      0.05
  2018-04-02  0        0
  2018-04-03  458      2.99
  2018-04-04  0        0
  2018-04-05  354      1.25
  2018-04-06  0        0
  </code></pre>