title: Replace specific values with NA for specific columns
body: <p>I have  a big data frame that includes binary (0/1) items. However some columns contains 3. I want to change these 3 with NA for certain columns and applying the changes to the original data frame.</p>
  <p>I have tries some solutions but they either applied to the whole dataset or creating a new data set with only the changes columns.</p>
  <p>head of dataset looks like:</p>
  <pre><code>                          X1  X2  X3  X4  X5  X6
                        S1  1   45  0   1   1    3
                        S2  2   12  1   0   3    0
                        S3  3   3   0   0   1    1
                        S4  4   11  1   0   3    3
                        S5  5   13  0   1   1    3
                        S6  6   20  1   0   1    1                           
  </code></pre>
  <p>Desired output:</p>
  <pre><code>                          X1  X2  X3  X4  X5  X6
                        S1  1   45  0   1   1    NA
                        S2  2   12  1   0   NA   0
                        S3  3   3   0   0   1    1
                        S4  4   11  1   0   NA   NA
                        S5  5   13  0   1   1    NA
                        S6  6   20  1   0   1    1    
  </code></pre>
  <p>Thanks :)</p>