title: Summary method results do not seem to be accurate for vectors
body: <p>This is puzzling me. When you run summary() on a vector of integers you don't seem to get accurate results. The numbers seem to be rounded off. I tried this on three different machines with different OS's and the results are the same.</p>
  
  <p>For a vector:</p>
  
  <pre><code>&gt;a &lt;- 0:628846
  &gt;str(a)
   int [1:628847] 0 1 2 3 4 5 6 7 8 9 ...
  &gt;summary(a)
     Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
        0  157200  314400  314400  471600  628800 
  &gt;max(a)
  [1] 628846
  </code></pre>
  
  <p>For a data.frame:</p>
  
  <pre><code>&gt; b &lt;- data.frame(b = 0:628846)
  &gt; str(b)
  'data.frame':   628847 obs. of  1 variable:
   $ b: int  0 1 2 3 4 5 6 7 8 9 ...
  &gt; summary(b)
         b         
   Min.   :     0  
   1st Qu.:157212  
   Median :314423  
   Mean   :314423  
   3rd Qu.:471635  
   Max.   :628846  
  &gt; summary(b$b)
     Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
        0  157200  314400  314400  471600  628800 
  </code></pre>
  
  <p>Why are these results different?</p>