title: Portioning '?' values based on Normal Distribution
body: <p>I have a dataset has more than 400000 observations. One variable has a lot of '?' values. Its factor table looks like this,</p>
  
  <pre><code> ?       AA     BB     CC     DD    EE       FF      GG        HH
  17082    247   1813    96     72    12529    49732   382188    9
  </code></pre>
  
  <p>I do not want to drop all '?' values, instead I want to portion '?' values to other factors based on normal distribution. For instance, while 'GG' factor should receive the most portion of '?' values since it has the largest factor, 'HH' should receive the smallest portion of '?' values. I cannot figure out how can I do that using <em>R</em>?</p>
  
  <p>I want to allocate 17082 '?' values based on normal distribution, then assign them corresponding factor.</p>