title: r Separate numbers with "/" in grouped data frame
body: <p>I have a large dataframe that looks like the following example:</p>
  
  <p>Say that there is a ball game, where you can throw the ball to hit a target and get points. There is a team A and B, and everyone can decide how many times they want to throw the ball (so this is unequal). It looks like this:</p>
  
  <pre><code>df&lt;-data.frame("ID" = as.factor(c(1,2,3,4,5,6,7,8,9,10)),
                 "Group" = c("A","A","A","A","A","B","B","B","B","B"),
                 "Number_of_hits" = c(1,2,5,3,3,1,2,1,1,3),
                 "Score_per_hit"=c("60","23.4/18.1","30/34.1/40/10.2/15.5","12/15.0/40","40/23.1/22","20.5","64.8/12.2","50","30","20/43.3/65"))
  
     ID Group Number_of_hits        Score_per_hit
     1     A              1                   60
     2     A              2            23.4/18.1
     3     A              5 30/34.1/40/10.2/15.5
     4     A              3           12/15.0/40
     5     A              3           40/23.1/22
     6     B              1                 20.5
     7     B              2            64.8/12.2
     8     B              1                   50
     9     B              1                   30
    10     B              3           20/43.3/65
  </code></pre>
  
  <p>Now, I would like to change it in a way that I can do something with the Scoring, so I would like it to be like this:</p>
  
  <pre><code>   ID Group Score_per_hit
     1     A          60.0
     2     A          23.4
     2     A          18.1
     3     A          30.0
     3     A          34.1
     3     A          40.0
     3     A          10.2
     3     A          15.5
     4     A          12.0
     4     A          15.0
     4     A          40.0
     5     A          40.0
     5     A          23.1
     5     A          22.0
  etc..
  </code></pre>
  
  <p>I have seen/tried some things with <code>str_extract</code> but I only get errors.. Could somebody help me? It's very much appreciated!</p>