title: Extracting a specific value from an ANOVA test in R
body: <p>I have performed an ANOVA test for a data with calcium content of materials using the code anova(calcium.aov) and obtained the following:</p>
  <pre><code>Analysis of Variance Table
  
  Response: calcium
                Df   Sum Sq  Mean Sq F value   Pr(&gt;F)   
  factor(batch)  4 0.096976 0.024244  5.5352 0.003626 **
  Residuals     20 0.087600 0.004380   
  </code></pre>
  <p>My aim is to extract the MSE (=0.004380) only, so I entered the code</p>
  <pre><code>anova(calcium.aov)[3][2]
  </code></pre>
  <p>But I keep on getting the error message</p>
  <pre><code>Error in `[.data.frame`(anova(calcium.aov)[3], 2) : 
    undefined columns selected
  </code></pre>
  <p>Is there a way to fix this?</p>