title: Frequency count of two column based on condition in R
body: <p>Hello i have two columns in an dataframe. Material number and supplier number. I would like to find out which material number is ordered from two or more suppliers?</p>
  
  <p>Following dataframe </p>
  
  <pre><code>OrderNo. Supplier Materialno
    1          LF       101
    2          LF       101
    3          LF       101
    4          DD       101
    5          DD       102
    6          DF       103
    7          DF       104
    8          DD       103
    9          DD       104
   10          AA       105
   11          AB       105
   12          AC       106 
  </code></pre>
  
  <p>I would like to have the result in this format</p>
  
  <pre><code>OrderNo. Supplier Materialno Count
  1           LF       101       2
  2           LF       101       2
  3           LF       101       2
  4           DD       101       2
  5           DD       102       1
  6           DF       103       2 
  7           DD       104       1
  8           DD       103       2 
  9           DD       104       1
  10          AA       105       3
  11          AB       105       3
  12          AC       105       3
  </code></pre>