title: R: how to add rows based on the value in a column
body: <p>I have a data frame that looks like this:</p>
  
  <pre><code>line = c(1, 2, NA, 4 ,5, NA, 7)
  group = c("1.0 Group A", "2.0 Group B", "3.0 Group C", "4.0 Group D", "5.0  Group E", "6.0 Group F", "7.0 Group G")
  df &lt;- data.frame(line, group)
  
  view(df)
     line    group
  1    1   1.0 Group A
  2    2   2.0 Group B
  3   NA   3.0 Group C
  4    4   4.0 Group D
  5    5   5.0 Group E
  6   NA   6.0 Group F
  7    7   7.0 Group G
  </code></pre>
  
  <p>What I want to do is to find all the NA value in the "line" column and place a row underneath that row in "group" column saying "Not Applicable". So that the new data frame should look like:</p>
  
  <pre><code>view(df)
      line    group
  1    1   1.0 Group A
  2    2   2.0 Group B
  3   NA   3.0 Group C
  4   NA   Not Applicable
  5    4   4.0 Group D
  6    5   5.0 Group E
  7   NA   6.0 Group F
  8   NA  Not Applicable
  9    7   7.0 Group G
  </code></pre>
  
  <p>I am thinking about using an ifelse statement or using case_when from dplyr. But I don't know how to work it out. Does anyone have any suggestion?</p>
  
  <p>Thank you!</p>