title: Create new dataframe that is larger than old
body: <p>first of all, thank you for everything you are doing. I am currently trying to wrap my head around a problem (new to r). I have a small n dataframe (e.g., <code>n=10</code>) but I want to have a new dataframe that consists of more of those observations (e.g., <code>n=15</code>). 
  The one condition is that I have to make sure that every value (i.e., row) of the old dataset appears at least once in the new dataset.
  Using sample, I could not achieve this - some rows were missing some of the times.</p>
  
  <p>EDIT Simple Example:</p>
  
  <pre><code>df = data.frame(matrix(rnorm(20), nrow = 10))
  df[sample(nrow(df), 14, replace = TRUE), ]
              X1         X2
  9    0.5881409  0.1967030
  2    1.1227569  1.9827646
  1    1.2225747  0.3428867
  10  -0.2780021 -2.3581644
  4    0.4687276 -2.2431019
  5    1.4592202 -0.6397336
  7   -0.8779913  0.4293624
  3   -0.1663962 -0.2435444
  3.1 -0.1663962 -0.2435444
  3.2 -0.1663962 -0.2435444
  1.1  1.2225747  0.3428867
  1.2  1.2225747  0.3428867
  6   -1.0797652 -1.1893041
  7.1 -0.8779913  0.4293624
  </code></pre>
  
  <p>However, we see that for example row 8 is missing.</p>