title: Adding observation to column does not work (Error: "subscript out of bounds")
body: <p>I am trying to add one observation to a data frame with just one column.</p>
  <pre><code>fitted.values.elec &lt;- rbind(fitted.values.elec[1:20,],5,725895,fitted.values.elec[-(1:20),])
  </code></pre>
  <p>Doing this I get:</p>
  <ol>
  <li>The error &quot;subscript out of bounds&quot;.</li>
  <li>The data frame turns into a matrix. For class() I get matrix and array.</li>
  </ol>
  <p>What do I miss here?</p>
  <p>Thank you!</p>
  <p>This is what I have:</p>
  <pre><code>  unique(fitted.values.elec[, 1])
  1                         5.858684
  2                         3.058384
  3                         7.387295
  4                         4.890524
  5                         4.969836
  6                         5.988356
  7                         7.337252
  8                         4.892035
  9                         3.980916
  10                        6.845760
  11                        5.118041
  12                        5.581330
  13                        4.492655
  14                        5.453386
  15                        5.914754
  16                        5.725895
  17                        4.105544
  18                        4.937531
  19                        6.246537
  20                        7.240994
  21                        3.968855
  22                        7.011589
  23                        3.606612
  24                        4.785006
  </code></pre>
  <p>This is what I want to get:</p>
  <pre><code>  unique(fitted.values.elec[, 1])
  1                         5.858684
  2                         3.058384
  3                         7.387295
  4                         4.890524
  5                         4.969836
  6                         5.988356
  7                         7.337252
  8                         4.892035
  9                         3.980916
  10                        6.845760
  11                        5.118041
  12                        5.581330
  13                        4.492655
  14                        5.453386
  15                        5.914754
  16                        5.725895
  17                        4.105544
  18                        4.937531
  19                        6.246537
  20                        5.725895
  21                        7.240994
  22                        3.968855
  23                        7.011589
  24                        3.606612
  25                        4.785006
  </code></pre>
  <p>This is what I actually get:</p>
  <pre><code>&gt; dput(fitted.values.elec)
  structure(c(5.8586839266439, 5, 725895, 3.96885481552305, 3.05838393273725, 
  5, 725895, 7.01158940397222, 7.38729508196495, 5, 725895, 3.60661157024705, 
  4.89052437902574, 5, 725895, 4.78500551267813, 4.9698364008177, 
  5, 725895, 3.96885481552305, 5.98835616438236, 5, 725895, 7.01158940397222, 
  7.33725247524616, 5, 725895, 3.60661157024705, 4.89203539822832, 
  5, 725895, 4.78500551267813, 3.9809160305324, 5, 725895, 3.96885481552305, 
  6.84575955265579, 5, 725895, 7.01158940397222, 5.11804123711197, 
  5, 725895, 3.60661157024705, 5.58132956152646, 5, 725895, 4.78500551267813, 
  4.49265477439422, 5, 725895, 3.96885481552305, 5.45338645418218, 
  5, 725895, 7.01158940397222, 5.91475409835944, 5, 725895, 3.60661157024705, 
  5.72589531680329, 5, 725895, 4.78500551267813, 4.10554371001916, 
  5, 725895, 3.96885481552305, 4.93753123438183, 5, 725895, 7.01158940397222, 
  6.2465373961208, 5, 725895, 3.60661157024705, 7.24099378881861, 
  5, 725895, 4.78500551267813), .Dim = c(4L, 20L))
  </code></pre>