title: Join dataframe to multiple lists
body: <p>I have the following list:</p>
  
  <pre><code>$df1
    x   y          z
  1 a 145 2010-01-01
  2 b  22 2010-02-01
  3 c  33 2010-03-01
  
  $df2
    x   y          z
  1 d  45 2010-01-01
  2 e  35 2010-02-01
  3 f 633 2010-03-01
  </code></pre>
  
  <p>I also have a data frame which looks like the following:</p>
  
  <pre><code>    x   y          z
  1 aty 451 2010-01-01
  2 b43 452 2010-02-01
  3 crf 343 2010-03-01
  </code></pre>
  
  <p>I am trying to join the <code>dataframe</code> by <code>date</code> of column <code>z</code> to each of the lists so the expected output would be something like:</p>
  
  <pre><code>$df1
    x   y          z  x.1 y.1
  1 a 145 2010-01-01  aty 451
  2 b  22 2010-02-01  b43 452
  3 c  33 2010-03-01  crf 343
  
  $df2
    x   y          z  x.1 y.1
  1 d  45 2010-01-01  aty 451
  2 e  35 2010-02-01  b43 452
  3 f 633 2010-03-01  crf 343
  </code></pre>
  
  <p>Data:</p>
  
  <pre><code>foo &lt;- list(df1 = data.frame(x=c('a', 'b', 'c'),y = c(145,22,33), z=c("2010-01-01", "2010-02-01", "2010-03-01")), 
              df2 = data.frame(x=c('d', 'e', 'f'),y = c(45,35,633), z=c("2010-01-01", "2010-02-01", "2010-03-01")))
  
  
  foo2 &lt;- data.frame(x = c('aty', 'b43', 'crf'), y= c(451,452,343), z=c("2010-01-01", "2010-02-01", "2010-03-01"))
  </code></pre>