title: Power Analysis in [R] for Two-Way Anova
body: <p>I am trying to calculate the necessary sample size for a 2x2 factorial design. I have two questions.</p>
  
  <p>1) I am using the package pwr and the one way anova function to calculate the necessary sample size using the following code  </p>
  
  <pre><code>pwr.anova.test(k = , n = , f = , sig.level = , power = )
  </code></pre>
  
  <p>However, I would like to look at two way anova, since this is more efficient at estimating group means than one way anova.  There is no two-way anova function that I could find.  Is there a package or routine in [R] to do this?</p>
  
  <p>2) Moreover, am I safe in assuming that since I am using a one-way anova power calculations, that the sample size will be more conservative (i.e. larger)?</p>