title: Row-wise Boolean comparison of data
body: <p>I have grouped my data by the appropriate grouping, and I need to be sure that "x" and "y" values equal each other for each unique combination of Group1 and Group2. In other words, what code could I use to cycle through this dataset and ensure that A1x == A1y and A2x == A2y, etc. </p>
  
  <pre><code>"Group1","Group2","group3","values"
  "A"        "1"       x       10
  "A"        "1"       y       10
  "A"        "2"       x       15 
  "A"        "2"       y       15
  </code></pre>
  
  <p>To help make the answer easier, here is the data.frame from the example</p>
  
  <pre><code>    d &lt;- data.frame(Group1= c("A", "A", "A", "A"), 
                      Group2= c("1", "1", "2", "2"), 
                      group3= c("x", "y", "x", "y"), 
                      values= c(10, 10, 15, 15))
  </code></pre>