title: Creating a new variable that contains conditional rowsums in R
body: <p>I have a dataframe with 12 variables:</p>
  
  <p><strong>id_group1, id_group2, ..., id_group11</strong> : 11 variables with a numeric value</p>
  
  <p><strong>mean_id</strong>: mean over all the above mentioned id_group variables</p>
  
  <p>What I would need now is a new variable that contains the rowsum only for id_group variables whose value is LARGER THAN mean_id.</p>
  
  <p>I am new to R and am still struggling with seemingly simple operations - so far I have tried using ifelse constructions but it never seemed to work.</p>
  
  <p>Does anyone have an idea how to go about this? </p>