title: Using dplyr to summarise values and store as vector in data frame?
body: <p>I have a simple data.frame that looks like this:</p>
  
  <pre><code>Group     Person  Score_1   Score_2   Score_3
  1         1       90        80        79
  1         2       74        83        28
  1         3       74        94        89
  2         1       33         9         8
  2         2       94        32        78
  2         3       50        90        87
  </code></pre>
  
  <p>I need to first need to find the mean of Score_1, collapsing across persons within a group (i.e., the Score_1 mean for Group 1, the Score_1 mean for Group 2, etc.), and then I need to collapse across all both groups to find the mean of Score_1.  How can I calculate these values and store them as individual objects?  I have used the "summarise" function in dplyr, with the following code:</p>
  
  <pre><code>summarise(group_by(data,Group),mean(bias,na.rm=TRUE))
  </code></pre>
  
  <p>I would like to ultimately create a 6th column that gives the mean, repeated across persons for each group, and then a 7th column that gives the grand mean across all groups.</p>
  
  <p>I'm sure there are other ways to do this, and I am open to suggestions (although I would still like to know how to do it in dplyr).  Thanks!</p>