title: Error with TukeyHSD
body: <p>I have a data which looks like below and I try to perform ANOVA and check the differences between all the columns. How significantly they are different from each other etc.   </p>
  
  <pre><code>df&lt;- structure(list(color = structure(c(3L, 4L, 3L, 4L, 4L, 4L, 4L, 
      4L, 4L, 4L), .Label = c("B", "G", "R", "W"), class = "factor"), 
          type = 1:10, X1 = c(0.006605138, 0.001165448, 0.006975109, 
          0.002207839, 0.00187902, 0.002208638, 0.001199808, 0.001162252, 
          0.001338847, 0.001106317), X2 = c(0.006041392, 0.001639298, 
          0.006140877, 0.002958169, 0.002744017, 0.003107995, 0.001729594, 
          0.001582564, 0.001971713, 0.001693236), X3 = c(0.024180351, 
          0.002189061, 0.027377442, 0.002886651, 0.002816333, 0.003527908, 
          0.00231891, 0.001695633, 0.00212034, 0.001962923)), .Names = c("color", 
      "type", "X1", "X2", "X3"), row.names = c(NA, 10L), class = "data.frame")
  </code></pre>
  
  <p>At first I perform ANOVA using the following command </p>
  
  <pre><code> anovar= aov(type~.,df)
  </code></pre>
  
  <p>and then summary the outputs as follows: </p>
  
  <pre><code>summary(anovar)
  </code></pre>
  
  <p>Which so far so good and it performs just fine. However, when I try to perform the TukeyHSD, it seems like I have structure problem. The error is like below. I searched and i could not find any similar situation. Any comment would be appreciated </p>
  
  <pre><code>TukeyHSD(anovar)
  # Error in rep.int(n, length(means)) : unimplemented type 'NULL' in 'rep3'
  # In addition: Warning messages:
  # 1: In replications(paste("~", xx), data = mf) : non-factors ignored: X1
  # 2: In replications(paste("~", xx), data = mf) : non-factors ignored: X2
  # 3: In replications(paste("~", xx), data = mf) : non-factors ignored: X3
  </code></pre>