title: Unnest (seperate) multiple column values into new rows using Sparklyr
body: <p>I am trying to split column values separated by comma(,) into new rows based on id's. I know how to do this in <strong>R</strong> using <strong>dplyr</strong> and <strong>tidyr</strong>. But I am looking to solve same problem in <strong>sparklyr</strong>.</p>
  
  <pre><code>id &lt;- c(1,1,1,1,1,2,2,2,3,3,3)
  name &lt;- c("A,B,C","B,F","C","D,R,P","E","A,Q,W","B,J","C","D,M","E,X","F,E")
  value &lt;- c("1,2,3","2,4,43,2","3,1,2,3","1","1,2","26,6,7","3,3,4","1","1,12","2,3,3","3")
  dt &lt;- data.frame(id,name,value)
  </code></pre>
  
  <p>R solution:</p>
  
  <pre><code>separate_rows(dt, name, sep=",") %&gt;%
    separate_rows(value, sep=",")
  </code></pre>
  
  <p><strong>Desired Output from sparkframe(sparklyr package)-</strong></p>
  
  <pre><code>&gt; final_result
     id name value
  1   1    A     1
  2   1    A     2
  3   1    A     3
  4   1    B     1
  5   1    B     2
  6   1    B     3
  7   1    C     1
  8   1    C     2
  9   1    C     3
  10  1    B     2
  11  1    B     4
  12  1    B    43
  13  1    B     2
  14  1    F     2
  15  1    F     4
  16  1    F    43
  17  1    F     2
  18  1    C     3
  19  1    C     1
  20  1    C     2
  21  1    C     3
  22  1    D     1
  23  1    R     1
  24  1    P     1
  25  1    E     1
  26  1    E     2
  27  2    A    26
  28  2    A     6
  29  2    A     7
  30  2    Q    26
  31  2    Q     6
  32  2    Q     7
  33  2    W    26
  34  2    W     6
  35  2    W     7
  36  2    B     3
  37  2    B     3
  38  2    B     4
  39  2    J     3
  40  2    J     3
  41  2    J     4
  42  2    C     1
  43  3    D     1
  44  3    D    12
  45  3    M     1
  46  3    M    12
  47  3    E     2
  48  3    E     3
  49  3    E     3
  50  3    X     2
  51  3    X     3
  52  3    X     3
  53  3    F     3
  54  3    E     3
  </code></pre>
  
  <p><strong>Note</strong>- </p>
  
  <ol>
  <li>I have approx 1000 columns with nested values. so, I need a function which can loop in for each column.</li>
  <li>I know we have <code>sdf_unnest()</code> function from package <code>sparklyr.nested</code>. But, I am not sure how to split strings of multiple columns and apply this function. I am quite new in sparklyr.</li>
  </ol>
  
  <p>Any help would be much appreciated.</p>