title: How do I specify an interaction in h2o.glm?
body: <p><strong>Background:</strong><br>
  In R, using a linear model, I could write a formula</p>
  
  <pre><code>est &lt;- lm(Y~1+A+B+C+D:A+E:D+E:F+B:A+B:D+C:A+C:D+C:B, data=mydata)
  </code></pre>
  
  <p>If "Y" happens to be binomial, then I can also write:</p>
  
  <pre><code>est &lt;- glm(Y~1+A+B+C+D:A+E:D+E:F+B:A+B:D+C:A+C:D+C:B, data=mydata, family = binomial)
  </code></pre>
  
  <p>But... 
  When I go to h2o.glm, I have to use the "x=.., y=.." form.</p>
  
  <pre><code>my_glm.hex &lt;- h2o.glm(y=y_idx,x=x_idx,
                    training_frame = "my_train",
                    validation_frame = "my_valid",
                    model_id = "my_glm.hex",
                    family = "binomial",
                    lambda_search = TRUE,
                    balance_classes = TRUE)
  </code></pre>
  
  <p><strong>Question:</strong><br>
  How do I add a formula that allows me to fit a generalized linear model (glm) with interactions using h2o.glm?</p>
  
  <p>Addendum:<br>
  I'm not sure what tags outside of 'r', 'h2o', and 'fitting' should be used here.  If you think of something relevant, could you suggest it in comments?</p>